There is nothing wrong with taking this approach, while you get yourself back on track. I've gone through this myself. Became an "asshole" in some peoples' eyes - "Why should I attend that social event? What am I going to get out of it? Nah, pass". They've gotten over it. So have I.
Truly though, who gives a shit, if that is what you need. Like OP said, it's your life. Do what you need to do for you. If you keep investing in things that suck the life out of you endlessly, it's going to drag you to a dark place, which is no good for anyone.
I trust selfish people more than I trust "selfless" people. Simply because selfish people are less likely to snap, and take out all of their repressed frustration at a seemingly random time.
It's taken me a while, but now I have a more diplomatic approach to extending my personal energy to benefit those around me, or invest in projects, work, etc.
You are right. It requires balance. However, you should not be afraid to tip the scales the other way for a while, so that you can refactor your priorities.