Great question!

A few thoughts on this:

1. In general, I like to use the stages of change model when trying to make a change. The research basically says that if people try to change when they're ready to change, they'll do it the first time, but if they try to change before they're ready, it will take multiple attempts.

For this reason, I try not to set action-based new years resolution (it'd be really suspicious if all the changes I wanted to make suddenly moved into the "Action" stage on the 1st). Instead, I'll do something like a "Theme" for the year (this year it's "Full contact with reality" and then take stage appropriate actions for that theme (thinking and reading during contemplation, planning during preparation, creating habits during action, etc.)

2. MurphyJitsu is a great tool to use here. There's a bunch of good exanations on LW, but the basic tool is to imagine you failed, ask yourself why, then patch your approach until it's very surprising that you failed.

3. Learning to forgive yourself is HUGE here. Research says that people who forgive themselves for procrastinating are less likely to procrastinate in the future, and I'm pretty sure this generalizes. Expect adjustments and forgive yourself for needing to make them.

4. If you're continually finding yourself with systems that don't stick, IME it's likely that you're fundamentally motivating yourself in a coercive way. You may want to read this post and sequence to begin to reorient your motivation system to a more sustainable strategy: https://www.lesswrong.com/posts/ga8g4RbKc6DmqEBwD/why-productivity-systems-don-t-stick

I've found it important to define habits as "daily-ish" unless there's an extremely good reason to Never Miss a Single Day *. That way you don't fall into the trap of the broken chain model where a single missed day dooms the whole project. You haven't failed if you start again. "Daily-ish" doesn't give license to just ignore the habit or make excuses, of course, but when you (inevitably) miss a day, it gives you just enough slack that you don't get fully derailed.

• Hint: there almost never is. Exceptions being, like, life saving maintenance medications or something. Unless somebody's gonna die, a miss is basically inconsequential in the long run as long as you get back on the habit as soon as you notice you've fallen off.

I am not very productive person, so take the following with a grain of salt:

If you fail, get up and keep going. Saying "I must do this 100% correctly, otherwise it is meaningless" is just setting yourself to fail... because sooner or later some random event will interrupt your progress... but it doesn't matter if you just lose one day and then continue with the original plan; assuming you actually continue (instead of "just one day" becoming your every day). In long term, perseverance wins.

Perhaps the proper way to think about this is that if you keep following your plans for ten days, and then fail on one day, those ten days still did something useful, and they also helped to establish a habit... not perfectly, but better than when you started from zero. That is, instead of feeling disappointed, you should focus on the fact that the second start will probably be easier than the first one (unless you needlessly make it difficult for yourself by overly focusing on the failure).

If you want to have multiple good habits, it is probably easier to introduce them separately, not all at the same time. (Exception: unless they are connected. For example, if one habit is "cooking at home, instead of eating at restaurants", and another habit is "eating healthy meals instead of junk food", getting both with one change is easier than making two separate changes.)

Sometimes, maybe your original decision was imbalanced and needs revision. Do you want to give up reading forever? If not, did you leave enough space for reading in your schedule? Reading at night is a bad habit, but having an "unproductive" day once in a while is necessary to recharge your batteries.

The "downward spirals of further failures" are a self-fulfilling prophecy, if you fear them so much that you never allow yourself a break, and then you burn out. You need to find a sustainable pace. And that pace may increase in the future... gradually. For now, focus on the fact that your average day in 2021 is quite productive, and that whatever you did once, you can do again.