When I stopped repressing the desire to live as a women after I realized that I was allowed to be happy.

To expand, it's not that I suddenly knew, it's just that the ridiculous amount of evidence — like the occasional inattentive/subconscious raising of my hand in school when girls were asked for, or the regular singing in my upper registers and head voice, or the cross dressing, or the huge amount of trashy chick flicks I watched, sometimes habitually (seriously, I watched 10 Things I Hate About You maybe 50 times in my teens...), or the self-inserting as the woman in porn, or slight cringing when being called a "smart boy", or the confusion when realizing I am attracted to men but don't want to be gay, or... — all of those things made sense as soon as I allowed myself to actually look for something that 1) could make me happy and 2) doesn't try to change my urges, wishes and desires. It's because I was a girl, and am a women. And even more, as soon as I accepted that, the droning suicidal thoughts in my head ("just smash your head with that window", "you should step onto the street", "hey, there's a bridge, jump", "you should stick a screwdriver into the wall plug", "go on, take the kitchen mixer and stick it in your eye", "hey that pencil fits in your eye even better", and so on...), which had been with me for over 15 years at that point in time, straight up stopped. They just up and left. They haven't returned in any significant capacity yet either — only when I start doubting it for longer than a few hours.

This realization happened about 6 weeks ago, and as you can see from my flair I'm somewhere in the 29 y/o spectrum.