I've been so incredibly lucky. I've had a really good education to a postgraduate level and I don't have any debts. I'm basically healthy; I don't have any long-term conditions. I come from a background that's well-off enough that I don't have to worry about making ends meet, but simultaneously I'm not so rich that I lose touch with humanity. I have time to read books, work on learning new piano pieces and pursue other hobbies. I basically enjoy my job most of the time and I feel like it's making some difference in the world. My boyfriend is great and I enjoy spending time with him. I love my family wholeheartedly and there's no one I have trouble getting on with. I live in a great city where everything's convenient to get to. I'm white, male, and it's not obvious I'm queer so I face very little prejudice.
So it's not any specific event, but I do feel hugely lucky and grateful. Honestly I feel like I should be doing more with what I've got; I feel like other folks have started with much fewer advantages than me, and have made much more of an impact than I'm making.