If it's someone I have come to respect/admire/like, although there may be some idealization built in, one hurt probably wouldn't be enough to dispel anything, depending on how egregious/malicious the behavior is.... I would generally have enough evidence of things I like to make an allowance for people's different moral actions and mistakes. I might even find it interesting, and wonder why they are acting the way they are, as I generally think negative behavior is triggered from somewhere. That said, with someone I'm close to, there comes a certain point where my feelings do tend to "immediately dispel"...the last straw. I feel that's more about self-respect than anything else. Why should I waste my time on someone who's going to treat me like crap, even if I have cared for them deeply? I can't control this reaction, per se... one day enough is enough.