+3

In addition to what Flan and Finewine have said, I will add - TALK! Talk to your SO about, well, everything - how you feel, what your fears are, how *they* are feeling, what would they like, etc. You've also got to be honest. Ask questions, even if they seem dumb. If you're asking it, it's not dumb.
Yes, the unknown is scary (Dani's heard me say that often enough

And since every transition is different, it's awfully hard to plan/prepare for "what's next." (I'm hearing an echo again....) That's all part of the talking

You're both going to have to compromise on stuff. In this way transition is no different than the rest of the relationship.
It is possible to survive transition as a couple. It's a lot of work, but I think it's worth it. Dani's transition has actually helped our marriage. We're a much more loving and closer couple now.
Good luck. We're here for you (and there's the chat too!)
WR