Lives ruined? Probably not. Friendships ruined? Hearts broken? Count on it.
You didn’t say whether or not you are in love, or even in like, with your boyfriend. And that’s what you first have to consider before you risk everything for a fling. Another consideration: Would it bother you if you found out your guy was mentally undressing your best friend? His friend is just a tempting distraction from the real problem: Is the relationship with your boyfriend worth saving? If not, go find yourself a guy who has your heart and a starring role in your sex fantasies. Or at least one with less attractive friends.

Stephanie Naman, Wendy Tatum and Ian David are authors of BarCode: Your Personal Pocket Decoder to the Modern Dating Scene. They live and write in Birmingham, Alabama and can be reached at barcodethebook.com.