How many times will you put up with your friends standing you up or canceling on you before you say "forget you!"? Well not say it literally, but you get the point. I know things do come up and they may have legitimate reasons to cancel but when it happens again and again and again, it gets kinda tiring.
I try to give at least three chances cause 3 is my fave number, heh. If plans don't pan out after three attempts, I stop making plans with them. They will have to take the initiative next time. What about you?