I personally don't think I need a reason beyond "I want to". There're a few dozen other reasons that factor into that, obviously, but ultimately that's all that matters- my life is my own, and I'll do with it what I want.
I could improve myself in the ways I'm supposed to. Take a million pills, tuck away my strange, ugly thoughts, work hard till I die, fit in better, have more intimate relationships, keep trying to fill the time before I die with a rapidly shrinking supply of things I find interesting and stimulating- maybe I could seriously pursue a dream, find success, etc.
Thing is- I don't want it. I don't want to live as a married man with happy children and a loving wife. I don't want to live as an acclaimed artist. I don't want to live like my 25 year old friend or my father or any man I know. I don't want to live like any woman I know, either. I don't want to be anyone. I don't want anything past today, let alone past age 30, as much as other people might enjoy their lives. It's been boring and tiring so far and I don't see it getting to be anything more. I've seen enough, felt enough, experienced enough of what the world has to offer. Seeing the ocean first would be nice, I think- but if I had a gun I'd do it tonight. As of this writing there is nothing on this earth that can hold me here.
I went on a bit of a tangent but anyways- the only reason that actually matters is "I want to" and you don't have to justify yourself to anyone