I tried coming out at 18. It didn't go so well. I told my best friend... who then never spoke to me again. It was embarrassing, we were doing the same training scheme and would bump into each other. He completely ignored me.
I was glad when that year was over, I went off to university and never saw him again. I do wonder about him sometimes, and did a little digging. He appears to have completely vanished.
After that, in my first year at uni I had an awful experience and nailed the closet door shut until I was 26.
I had a seizure that was... misunderstood by the people I was with and my own escape was to clam up completely about it for some years.
I did eventually talk to a therapist who gave me a good explanation, it just took some time.
Have to admit, I regret doing it most of the time right now, but it doesn't change who I am. (I know it gets better! That's what I'm waiting on.)
I've been quietly bi for decades, answering honestly when asked, but not discussing it outright. I married a woman and was straight-passing.
I've been closeted trans for much longer, and the people I've come out to have mostly responded with disgust. Apathy at best.