I wish I'd started HRT sooner. If you feel certain, start it; you'll know fairly quickly if it's not for you. And it takes sooooo long for any changes whatsoever.
I've been on it since November of 2025, and I've only experience some emotional changes, minimal breast development, and other, more mild physical changes (which could be placebo; not sure).
During this time (and kinda for a year—two years?—prior) I've worked on voice training, exploring presentation, and social transitioning (i.e. coming out to people).
I can, of course, stop the all of it at any time, since it's all behavioral. Except HRT. The longer I live as a girl, the longer I become one. Every day, I become more certain of my decision, and every day, the changes caused by HRT increase.
Of course, this is just me: you do you.
Get a therapist though, if you can. They can make a world of difference. Also friends. They're great too (even if they're mostly online, like mine). Support is everything.
Have fun exploring! <3