when they don't care what their actions might cause you to do
The second time. I had a friend who texted me out of the blue once claiming our friendship would hurt us and that I should move on. I fought for her the fist time and we patched up. The second time she did it. I no longer needed to fight. I knew our friendship didn't matter enough to her to keep her psychotic demons from dictating such stupid texts..
When you feel the time is right i guess.