For me it was when I came face to face with his infidelity. I had suspected he was fooling around for a few years, but I am not into "spying" or checking up on his whereabouts constantly, and I think I really didn't want to know the truth.

But once I found out for sure, I said "this is the end of the road for me." I am very proud of that moment. It signaled the start of my not willing to be a doormat anymore.