How to overcome fear of transitioning?

Hey. This is a repost, the original title was "How to stop being a coward?", but I decided I should have a bit more self respect and not buy into what the nasty voices say as much. Most of the post is unchanged otherwise, but I felt it was important to change the title anyway.

As of a few months ago I'm trying to transition, but I'm having a hard time with it. I've known something was wrong for years, figured out it was almost certainly gender dysphoria when I moved out of home, and then promptly ignored the problem for the next two years. Why? Because I'm afraid, and I'm not sure how to shake it.

I have a lot going for me. I've told my best friend and psychologist, both of whom are supportive, I'm lucky to live in a place where being trans is not illegal (and not too far from me there is an informed consent clinic), and I'm making enough money at work where I have a bit of cash saved up for various trans-related things I'll inevitably need to buy. Despite all this, I can't bring myself to move any more forward than I already have.

Maybe it's a consequence of being in the closet for so long and knowingly ignoring the problem, maybe it's that my family isn't supportive, maybe it's my autism not wanting things to change, but I just feel like I'm in limbo and I can't take the big steps towards feeling like myself. Some monkey-brain part of me is scared of what could happen if anyone else knows I'm trans in real life, and it's genuinely frustrating knowing what I want and how to get it but just not doing it. And I feel like the more I put it off, the more I'm watching myself turn into a man, and the more work it's going to be to get where I want to go. And that also ties into a fear that, maybe, even if I work up the courage to transition, I'll end up "doing it wrong" or it won't actually make me feel any better.

Surely I'm not the first or only person experiencing this, and surely some of you have overcome this (or at least learnt to deal with it). Anyone have any advice? I'd really appreciate anything you think might help.