I’m sorry to hear that. What helped me was finding (after many years) a non-denominational church where I could get a community and weekly lectures on morality but without the supernatural baggage.

Good luck!

There's this bit from Chandler's "The Long Goodbye", one of my favorite books:

"Maybe I can quit drinking one of these days. They all say that, don't they?"

"It takes about three years."

"Three years?" He looked shocked.

"Usually it does. It's a different world. You have to get used to a paler set of colors, a quieter lot of sounds. You have to allow for relapses. All the people you used to know well will get to be just a little strange. You won't even like most of them, and they won't like you too well."

With losing faith I imagine it's like that too. There's no longer a voice booming at you that you must avoid death, or behave morally or whatnot. From now on, the motivation has to come from you and from the world around you, and it'll be quieter at first. You won't find it in one philosophical swoop (and I'd be wary of anyone offering you such a swoop: you're vulnerable right now). It'll have to come gradually, in time. Just give it time.

"I'd rather be sad than wrong."

What's helped me is to realize that "sad" and "wrong" are different dimensions, and don't need to be correlated at all.

I grew up in a less-community-intensive church than LDS, and my intellectual beliefs have been purely atheist since my mid-teens. My professed beliefs among some groups of family and community is more agnostic, and I'm very comfortable with others believing things that seem unlikely to me, as long as we can still cooperate in having fun and improving the world (which means I'm not part of groups that demand explicit declarations I don't believe).

Happiness for most humans does require community and love from other humans. It may or may not require (it doesn't for me, nor for a lot of people I know, but it could for some) having a strong belief in supernatural meaning. Helping to improve the lived experience of existing and near-future-probable-humans is meaningful and wonderful. Reality is enough.

But don't sleep on community and personal relationships. These often require compromise and even some unresolved disagreement on things that seem important. From what I can tell, LDS is among the more effective community-building religions, and does seem somewhat accepting of socially-compatible unbelievers.

https://www.lesswrong.com/posts/x4dG4GhpZH2hgz59x/joy-in-the-merely-real

Knowing truth doesn't provide, by itself, human connection. In the Mormon church you had a community, people with whom you interacted and had a common ground, shared interests, and collective goals. When one breaks with such a community, without having first established a new one, the result may be extreme loneliness.

The way to fix that is to find a new community. Many atheists and rationalists schedule periodic meetings to interact with each other and talk in person, so depending on your need of connection that might suffice. If not, there are church-like organizations that require no profession of faith and welcome atheists, which is particularly effective if one's been raised with church attendance and miss that. In the US Unitarian Universalism is one of the oldest movements along those lines, with the form of Protestant Christianity minus the belief system, but there are others. This CBS article lists several: Inside the "secular churches" that fill a need for some nonreligious Americans.

If you're not particularly attached with atheism itself, you also have the option of exploring personal religiosity and communities that go along with those, which basically means constructing your own religion from your own experiences, which can be induced through mean ranging from meditation and self-suggestion all the way to psychedelic trips. Doing that while remaining 99% a rationalist isn't particularly difficult, the cost being embracing compartmentalization. But then, if that's what it takes for one to find enough meaning in the world that they want to continue on it, I'd say it's a price well worth paying. It's what I myself do, and it hasn't caused me any major problem, my take simply being that, if what I perceive is true, science will eventually catch-up, and if it isn't, as long as I'm not trying to assert it above the perfectly legitimate skepticism of others, then shrugs.

So, my suggestion, in order, would be: meet other atheists and rationalists in real life with some regularity; if that isn't enough, try a church-like atheist/agnostic/agnostic-friendly community; and if that still isn't enough, do your own thing with others doing similarly.

One of the nice things about realizing that you're Douglas Adams' puddle is that the nature of cosmic reality doesn't have much to do with what you have for lunch. I think if you frame things more concretely, your questions will be more answerable.

Don't you want things? What do you want?

Why you want those things has to do with your particular circumstance, but this is probably what you believed before. And if you start thinking about what you want, as opposed to what you should want, you may find that it's not a simple and unsatisfying thing, but that there's a lot of depth there. And I suspect you'll find also that what you want is sort of warm and fuzzy and prosocial. These things seem to be in most of our firmware. Tautologically, I like that.

If self-reference isn't satisfying, and you want grand cosmic majesty, I think that if you look up at the sky and keep asking why, you will find plenty of wonder. Tegmark thinks that all things which can be, are. Can we ask for more?
 

Also, I'm happy to chat anytime if you ever need someone to talk to.

Why should anything matter if we're just arbitrary self-reinforcing arrangements of chemicals? Why should I avoid death if it's just the chemicals finding a new arrangement?

I don’t think I had identical experiences (I stopped believing pretty young), but a few things helped me with adjacent considerations:

• I realised that what makes my life meaningful has always been deeply rooted in physical reality (happiness, caring, friendships, etc.). Think of someone you care about, what has changed? Have they become less important? Do you want them to live any less? For me it had not.
• I had to recalibrate my expectations. For example, taking philosophy classes (well, mainly the discussion with peers around philosophy classes) made me realise that I had previously naive conception of knowledge as 'believing true things'. I remember a brief period that felt something like "Oh my god, we can't know anything". This didn't last long. Now I don't think that 'naive' level of knowledge is really possible, but knowledge is still important and valuable. 
• I always had doubts. I never 'truly, truly' believed in an afterlife, but lots of people who believe in an afterlife also doubt (a) whether it exists and (b) whether they’d qualify. You've likely always lacked full conviction, now you lack (much) more of it. You've been able to deal with this uncertainty before and may already have psychological skills to apply to this. [Just don't think about expected value and infinities here!]
• One additional consideration: Do you always feel this way? Or mainly when you're sad, moody, depressed? If it's the latter, it might be worth it to consider whether some of the intensity of these questions is amplified by your mood, and whether CBT-like exercises might help you separate the philosophical question from the emotional weight.

Why should anything matter if we're just arbitrary self-reinforcing arrangements of chemicals? Why should I avoid death if it's just the chemicals finding a new arrangement?

Let me propose a new theology. God and souls are real, but God only cares about order, not good; and souls die with the body. Nonetheless, souls are the only thing in the world that can understand good, and is capable of acting in favor of good (or evil). I think that would be truer to the nature of reality than the depressed materialism that you have landed in for now. The fact is, reality is not just atoms, it's also mysteriously persistent order; consciousness exists, and it is still unknown how it relates to the world of atoms; and, we do have something like a moral sense, even in the absence of a benevolent deity. Philosophy can replace religion, and then all you need is the vital energy to act in the world again. 

This may be totally not helpful or not working for you/anyone; for the small prob that it might be slightly helpful, I post it without having had time to think about it enough myself.

First, if I read you correctly: Diagnosis $2 suggests you've gone one step further than the 'classical' non-religious: philosophical illusionism or something of the sort: something like 'after all, it's all raw physico-chemistry, not actual spirit or actual ultimate moral worth or sth'.

I at max half share the religious-desillusionment (christian as child but rejecting during adolescence, w/o bigger crisis as I grew up very modern 'not care' christian), but I empathize with $2 a lot: when I think about it I attribute a lot to 'pbly actually it doesn't really matter', 'we're a bit more empty machines than we admit; proudly making up our importance'. That said, I consider myself lucky (so far!^[1]) that emotionally I simply don't fully buy that and am so far emotionally invested in my and others' lifes just as much as before I took illusionism - again, sort of mostly intellectually-only - more seriously.

So fwiw how I 'see' things and am 'happy' with it - to the degree that it's not 100% ridiculous to summarize that in a few words in a fwe min - and even if anyway all remains fuzzy fuzzy fuzzy:

• Do you like to feel connection to people? Do you like to see the world through the emotional lense just the way you've always used to do, when you were more fully 'believing' in all of it? Do you like to try to invest yourself to making society, and/or specific other people happy? Do you like to try to be the 'best of yourself' for (i) your future self, (ii) those around you, (iii) the broader society, (iv) other [supposedly? actually?] animals?, (v) maybe in future even AIs? Even if we're partly, hugely, egoistic, we can try to do a reasonable compromise between our conflicting aims and try to err on 'doing good' whenever we can convince ourselves to do it - without reproaching when we fail - simply to the degree possible and even if totally failing simply trying at least a bit, all times.
  • Then, maybe you can try to continue living life with such attitude; making yourself happy not least by trying to make others happy and reaching drive from trying to be a good little puzzle in the difficult and for many so so disastrous world?!
• Even if ultimately it turns out it doesn't 'really' matter, you've not lost anything trying to do as if it did matter?!

I could see this fail if e.g. you've got really deep dissatisfaction/pain in you, i.e. if life sucks truly with little hope in getting joy. Then the next best thing that comes to mind is mindfulness/meditation. My flavor would be Sam Harris style; imho totally non-pretentious; based on a real attempt in trying to understand the mind/world without much spooky stuff; even if there's an assumption clearly that there's something that has ultimate value; I think in caring yourself you do actually attribute that value to your consciousness yourself even if you're right to question the absoluteness of it all.

Even if this is not helpful - sorry! - I'd be keen to see what it invokes in you if you don't mind sharing! Of course, you can also ignore (or even delete if you think this is too obviously unhelpful and tangential).

1. ^{^}

   Crisis in the making? I attribute significant prob to something like that, though so far rather none in sight. Even the dissonance doesn't often actively strike me so much - again, only theoretically. Maybe until I'm once less busy busy with daily small things..