What to say now that I have agreed to mediation?

Nothing special. I'd just walk along the path she is going now. Otherwise "go climbing". Great to read that you don't feel as much fear as before. I have similar experiences: some situations were I had a certain amount of fear don't trouble me any more. Compared to the separation everything else just pales.

I have put the "go climbing" in quotation marks because it can also be seen figuratively: you confront the mountains in your life - and you find your way no matter what.