I think my surety in this matter just comes from the fact that I've never felt comfortable anyway.
Even if I'm wrong, I won't have left a 'comfortable place' (or identity) to end up in an uncomfortable place. It'll be a new place, if nothing else, and even if it's still uncomfortable. I'm prepared for it to be as uncomfortable as I feel right now, but hopefully, it won't be... and will actually be an improvement.
Honestly I can only shrug to myself about my situation and ask why not? The only reason why not would be if I wanted to continue on along this road that is not the one I want to be on, and as Trinity says in the Matrix, "you know where that road goes, you know exactly where it ends." Some people might feel better knowing the road and where it ends, but I don't. The thought I'll die on that road isn't one I'm happy with.
Sure, I feel uncertainty about the details... but really, the details aren't so important. I'll figure out using the bathroom and the clothes, speech and mannerisms and whatever else. I don't have to change into somebody else, I just have to relax.