Every dollar I spend on myself is a dollar that could go much farther if spent on other people. I can give someone else a year of healthy life for about $50  and there's no way $50 can do anywhere near that much to help me. I could go through my life constantly weighing every purchase against the good it could do, but this would make me miserable. So how do I accept that other people need my money more without giving up on being happy myself?
For me the key is to make most choices donation neutral. As money comes in I divide it into "money to give to the most effective charity" and "money to spend as I wish". How to divide it is a hard and distressing choice, but it's one I only have to make once a year. Then when deciding to buy something (socks, rent, phone, instruments, food) I know it's money that isn't getting given away regardless, so I don't have to feel constantly guilty about making tradeoffs with people's lives.
Julia and I have been using this system since 2009.  It's mostly worked well, but it's needed some additions. The main issue is that declining to spend money on yourself isn't the only way to trade off benefits to other people against costs to yourself. For example you could decide to be vegan, donate a kidney, or cash out your vacation days and give away the money. For ones that generate money directly (cashing out vacation) the solution is simple: that money goes into the pool that can't be given away. For ones that don't generate money you would convert them into money via the good you think they do. Take the most effective charity you know about, figure out how much you would need to give to them in order to have the same positive effect, and then move that amount of money from donations to self-spending. For example, I might estimate that giving $100 to the AMF does about as much good as being vegan for a year, so if I decided to go ahead with being vegan I would decrease my annual donations by $100 and allocate another $100 to spend on myself.
I may or may not decide that having another $X to spend on myself is better than sacrifice Y, but whichever way I decide I'm working to make myself as happy as possible for a given amount of doing good. It's not a choice that has additional lives saved weighing on either side of it.
(This doesn't deal with a potentially important category: things that only make you somewhat unhappy. For example, working a higher paying job you like less, or pushing yourself to host more effective altruism meetups than you'd really like to. I don't see how to deal with this, but I don't think it's been a problem so far.)
 Specifically, I can donate to the Against Malaria Foundation, which distributes anti-malarial nets. The main effect is averting deaths of children who will probably go on to live around 30 years once you take into account other things they might die from. This comes to about $75 per additional year of life. There are also many other people protected by the nets where it doesn't make the difference between life and death but helps them live healthier lives. That brings the $/DALY figure down to about $50.
 I also wrote about this approach in 2010 when it was much younger.