My biggest fear going into transition was that my family was going to reject me. I cared about their love and approval so much. It took 2 years, but the fear came true, my dad did stop talking to me and break contact with me. Frankly, though, it turns out that family rejection by the point in time where I was long since past even remembering what it was like to be male, and was long past that "OMG is it even worth it?" phase meant that it barely even hurt when it happened. So that "greatest fear" ended up being nowhere near as bad in real life as I was afraid of.
My other biggest fear was that I'd be an ugly woman, or that I'd never pass even though I was starting hormones relatively early in life, age 27. Other people constantly mocked me going into transition because I was such a huge ugly guy that nobody thought I could possibly succeed. I tortured myself with those hurtful words too. So that fear didn't start going away until VERY recently, about 28 months into HRT, even though I'd been getting gendered properly for almost a year before that. It takes a LONG time to erase a deep-seated fear like that.
So since those were my two biggest fears and they ended up unfounded because I survived them, my only other significant remaining fear is that even post-surgery nobody will be able to see me as an attractive woman and want to date me and snuggle with me. That one I'm still working on, and still afraid of. I haven't really tried dating yet because I'm still dealing with too much genital dysphoria to enjoy intimacy, and thus I don't want to drag someone else into my genital dysphoria issues, but post-surgery I'll get back to you on that. And hopefully as with the other fears, the fear of it happening will either be completely unfounded or nowhere near as bad as I was afraid it would be even if it's true.
