One of the reason's I've been thinking about maturity is that my life has been going through major changes.
Only three weeks ago I got married, and late last year, I moved to New York City. I feel settled, and more or less at peace with myself.
A little less than ten years ago I began an extended period of stress, depression, and change. It started with me having doubt about graduate school, but added a personal dimension (relationship stuff) soon afterward. That's probably not coincidence, it's hard to be going out with someone who's having a midlife crisis, or at least a mid-20s crisis.
It's an obscure Foundation reference (see Isaac Asimov at the wikipedia) but I grandly saw this as a conjunction of professional and personal crises.
I'm not going to talk about it in this entry, but the next six years or so changed me. To be honest, I miss the sharp feeling of growth, and learning, that I had during that period, but I don't miss the self-doubt and uncertainty about myself.
For the last couple of years, I've felt the same about the world and myself, and having an increasing awareness of whom I am, especially since I'm not changing so quickly now.
If you look at my previous entry, you'll understand that I think I've turned into a mature ecosystem. I understand, and accept, how the different parts of my personality interact.