A good example of this idea is this very journal. More than anything else, I write in here for myself. I enjoy getting comments, sure, but mainly, I write to express myself for myself. I find people often write with more interest and the results are better when they write for themselves, not someone else. I know my writing in here is no master work of English literature, but it feels good to get out.
Another example is art. Right now, I'm doing, of all things, a piece made using crayons and turpentine. It's simple and a lot of fun to work on. I really like the effect this new medium has. This picture isn't an assignment, the medium was not a requisite, I'm doing it merely because I felt like it. I'm really enjoying it, too, even if it isn't my finest work.
I started to learn Japanese about 6 months or so ago, as most of you know. It was by no means required of me. I don't have as much time as I'd like to, but when I have the time, I really like learning and practicing. When I am able to translate just a line of a song or a short dialogue in an anime, it makes me happy, because that's the kind of thing I've been working to do. I do it simply for my own happiness. Atashi no shiawase.
I try not to be self-centered, and I really enjoy doing things for other people. Still, it's the little things that I do on my own that really help me get by some days. I think everyone would be at least a little bit happier if they took time to recognize what it is they like to do for themselves, just themselves, and do it.