I get the pang of "D'oohhhh, why didn't I act on this when I was 24/29/19/3/not now?" sometimes, and you know, you gotta own that part of the experience. It sucks when you spend so much time meandering aimlessly through the loosely-constructed jam-session of your adolescence, to finally come up with a good tune after your audience has already walked out. But that's the thing: that tune, that catharsis, that realization of exactly who you were and what you should be doing, that would not have shown up without the 30-minute jam session. We were constructed, both by nature and nurture, to be and behave in a certain way; civilization has historic institutions revolving around its often-antiquated demands from us. It takes a very, very long time to unlearn these things, to pierce through the smoke and actually get a clear view of what's going on inside you.
When I realized I was trans, it hit me like a bolt of lightning. I seriously jumped out of my chair. All that idiosyncratic behavior, all those bizarre whims and rituals and desires that the ebb and flow of daily life so easily kept under the tide, all those suddenly made complete sense. I would have never figured it out if I hadn't met my... well, now ex-girlfriend, and I wouldn't have met her if I hadn't spent so much of my life trying to be a cis-hetero male like God and Country intended.
It's a process, and you can't beat yourself up over it. Some of us just have longer roads than others. Doesn't mean I'm not jealous as ->-bleeped-<- of someone who transitions at 18, but they're going to have their road ahead of them too. It doesn't matter when transition occurs in your life, what does matter is that you have the courage to act on truth as it's revealed to you.