Been there, done that, until I completely burned myself out and needed months to recover from it. Being there for others and not for yourself although it might be rewarding at the moment really isn't that rewarding in the long run. I was really depressed for a long time as a result of being there for everybody else but not for myself.
As for the fundamental changes, well, they are tied to what I was saying previously, I realized that will not last much longer if I don't dwell on what I need and what I want, so I spent some time with myself and got to the conclusion that I really don't want to have kids any time soon (meaning in the next several years), that I want more from others, and I'm really enjoying my work at the moment. Fundamental change is that I managed to be happy for a lot longer than I have been in the last few years and I'm all into sustaining that goal. I een started losing weight which for me is a really big sign that I'm on the right track, that I'm dealing with positive stress rather than just negative one.