That is not correct. I have a good friend who "stepped over the line" (his term), regretted it and never did it again.

You (and most commenters) covered half of the issue saying that you have to be true to yourself and your vows. Very true.

People rarely think about the other person. Whether it is a one-night stand, an affair, or a totally non-sexual relationship, there are two sides.

Let's say you slept with Nicole and then realized it was a mistake and told her so. She might not take that well. She might threaten to tell your wife. She might call the police and claim you date raped her. She might call you in 3 months and claim you are going to be a daddy in 6 months.

Like with an argument or even a disagreement, the other side gets a say. Assuming incorrectly that you know how they will respond has led to many a breakup, divorce, law suits and even wars.