I am glad you feel a bit better.
I don't know what other things you want to grow in ability, but coping with big disappointment/grief definitely comes up for you a few times. The only way to avoid the risk of breaking up with people is to not date at all. So really you have taken the risk already as the price of admission to dating. Not just her, but dating in general.
As for not being devastated, I'm not really sure how to do that. Truly giving my heart to another person is huge for me. If that comes to an end, it's going to destroy me a bit. It always has and I'm not sure I've changed that much for it not to. When you plan a future and intertwine your lives together, that's a painful break no matter how you plan for it.
Of course it is painful.
It's not about avoiding ALL pain and making it ZERO pain. It is about REDUCING pain to minimal if it has to happen, and really it's one of the most loving things one can do.
I don't know how YOU do it. I know how I do it.
Me? Should it happen, I don't want to be up the creek without a paddle -- no plan, dealing with emotional upset, etc. Between
- upset and no plan and added stress of making plan while upset with upset partner
- upset with plan made while we were calm to hand to help move it forward OUT of the upset?
I'll take upset with plan to move it forward!
And the process of planning it so it can go well? In my experience it actually draws people closer and it is reassuring. Ups the odds of it not being needed and ups the odds if it going well if it ever IS needed.
Because who wants and loves to experience a break up going WONKY?
Could learning about the grief process help demystify it not be so scary? Could google "stages of grief."
Could you be willing to talk to her about "how we want to break up... if we have to break up? What kind of exes will we be?" Or you need to talk about it with yourself more or others first before talking with her?
Could listing what other abilities/resources you would like to have before going there help? Or abilities/resources you would like her to have?
Hang in there! Keep thinking your stuff out.