um..how do you balance forgiveness with having boundaries?

The question alone probably reveals the flaw in my logic to some of you clever folks. Please enlighten me to the errors of my way.

As a youngster, I didn't put up with shit. If we were dating and you 'crossed' me, that was it. But thats pretty my way or the highway, yeah? It certainly walked me out of more relationships than not. Somewhere I got to thinking I needed to be more forgiving. People fuck up, right? I need to give them the room to fuck up as much as I need the room to fuck up. But I think somewhere along the way I got myself turned around and started interpreting that as not having boundaries. I 'forgave' shit that I would have left them for when I was younger only to find that became a pattern that I left them for later.

So. How do I stand my ground..er..not that actually. How do I distinguish offenses from fuck ups? Does that make sense? How do I distinguish an honest 'mistake' from the beginning of the end? Patterns, huh?