Trying to grow a backbone!

[Virtually_Handsome]

I don't know what's better, having the ex available for sex, or just having to make a clean break.

Really?
One might feel better in the short term, but it's just dragging out the pain, and making it harder to detach your emotions from the X's actions.

Especially since you already know this:

Anyway, if that started up again then the whole destructive relationship cycle would start all over again.