an honest mistake?

Is cheating an unforgivable offense?

The answer might not be as straightforward as you think. In this CNN article, a psychologist says infidelity doesn't have to end a marriage.

Growing up, even through college -- as in, like, four years ago -- I told myself that any guy who cheated on me never deserved a second chance. Even if it was just a one-time deal. But since then, I've met friends who have stayed in relationships amid infidelity. For a variety of reasons: kids, the sanctity of marriage and sometimes just plain relentless affection.

And influences like "Sex and the City" -- a show that many women regard as the Bible of relationships -- seem to support the idea that infidelity can, at times, really be just a mistake.

A couple days ago, my mom asked me if I'd ever stay with a guy who hooked up with a prostitute. My answer was something to the fact of hell no. My mom's response? Surprise. "It's not like he'd be forming an emotional commitment," she said.

In which circumstances, if ever, would you be able to regard cheating as a forgivable mistake? Even if you can forgive, is cheating something you can ever really forget?

Oh, and one more question for you guys: "Once a cheater, always a cheater." True or false?