I happen to be mtf trans and I wish I had transitioned earlier. Sure I pass without issue, and am completely stealth, some people even think cute, I started hormones at 23. I should have just went to middle school wearing a dress but I was a stupid coward due to living in the south, daily experiencing harsh bullying even from teachers (had a teacher furious at me for crossing my legs) and my parents were very harsh when I tried to tell them at 11. They still don't accept me though claim they are open minded people who hate bigotry. I was given the option to dress as a girl in 7th grade for halloween but I was too nervous to say yes. To this day and the day I die, I will never forgive myself hence why I sometimes starve myself. Wish I was born into one of those supportive families, but I guess I'm not worth anything. Sadly, I don't even have any friends to really fall back on for support.
Also I wish I took up piano when I was young. I feel like I'm playing catch up learning in my 20's. Sure, I learned how to play some great pieces like Howl's Moving Castle, but if only I had started earlier instead of watching TV shows I didn't like. It would have been a good outlet considering how much my life was hell back then.
I would add in all the years spent working on my writing, but I just landed a literary agent for my trans teen novel. Sure I like writing, but the constant rejection letters over a decade saying how good of a writer I am, but too niche was crushing. With this latest manuscript, I've gotten a lot of positive responses from other agents. My agent thinks she knows some publishers who would be interested. My parents refuse to read any books trans related, but maybe just maybe they'd read this one. Perhaps something can go right in my existence.