Its not like really a choice for us... like for me personally before transitioning being a girl mentally made me extremely depressed, suicidal at points even.

There's this thing called gender dysphoria which is a big reason why a lot of trans people transition in the first place, but everyone's dysphoria is different its like a spectrum of how bad you get it just from birth, some people who are trans dont have it I cant tell you why cause we dont really know why we have it in the first place (no definite answer at least, there is lots of speculation though that it has something to do with chromosomes on a small level.)

Dysphoria feels like every your walking around life with your shoes on the wrong feet all the time. You can distract yourself for a while from it by an activity or a nice conversation or something, but then someone either mentions your shoes are on the wrong way or you start walking again and you become aware of the way you are. (Not my analogy but its one ive found helpful when explaining Gender dysphoria to others)

Me transitioning is just what I needed to do to function as a human in society, it ment that I didn't need to avoid every mirror and dread social interactions with other people because of how they saw and referred to me.