I just don't remember the last time being this hard. All I wanted was HIM. That's it.
Because you didn't do it the right way last time. The right way is ALWAYS more difficult.
Look, Train -- at some point, you've GOTTA trust him. Yeah, it's "trust -- but verify" -- but you either are willing to open up your heart to him one more time or you're not. You've let him know what your stone-cold dealbreaker is (do it again and I'm OUT -- PERIOD), so let that lie and work with the man.
I totally get your fears. I had them too, for a good 2-3 years after my wife agreed to reconcile. And I STILL get triggers from time to time, no matter how good things are now between us and no matter what she writes in my anniversary cards and such. It's natural.
Slow and steady, and communicate to each other your fears and concerns. I think Retrouvaille would be an AWESOME thing for you two right now, because it really focuses on communication more than anything else. I hope you'll consider it.