I've been loathe to post anything on this thread, feeling like a bit of a hypocrite.
Yes, I have cheated in a relationship, once. Not while I was with my husband now, a previous relationship. I've also been cheated on. That road CPL4Life spoke about is a slippery slope indeed, and I agree that it's important to recognize those road signs. I will say, and it's no justification whatsoever, the relationship was doomed from the get go. The ex declared that he wanted to be able to sleep with whomever, but I couldn't. So he did. With his ex, and one of his female friends, and lord knows who else really. Why I stayed as long as I did (too long) I'll never know. And I suppose out of spite, I stepped out on him. Big red flag! Should have just left instead of staying to cause further damage. Spite is a nasty thing.
I call it a very low point in my life that I have made a conscious effort not to revisit. Do I get tempted? Of course, I'm human. I will admit I like eye candy as much as the next person. I just make it a point of looking but not touching.