[The adulteress] gives no thought to the way of life; her paths are crooked, but she knows it not (Proverbs 5:6).
I believe that very few people go into an extramarital affair with malicious intentions. The people who get caught up in such situations are usually not out to hurt their loved ones. No one's out to break up marriages and scatter families. If I were to look at things from the side of one who might have been betrayed, I could understand of course, how it might feel like the "other woman" or the "other man" is a soulless, vindictive, home-wrecker... But really, I would guess that this is rarely the case.
More often, extramarital affairs are simply the result of carelessness. People somehow find ways to disconnect their actions from their potential consequences. We've all read the books and seen the movies; we all KNOW that these things end up badly, with someone (or everyone) getting hurt. Still, in our longings for affection, affirmation, and acceptance -- grasping for love, wherever we can find it -- we're susceptible to disregarding the writing on the wall and falling through the same traps again and again because we just don't think things through.
Proverbs 5:6 reminds us that we need to continually check our lives for blind spots. In which ways am I (subconsciously) setting myself up for a mistake? Or which people in my immediate surroundings might be dangerous for me? Not that they're sneaky or predatory or malevolent at all -- actually quite the contrary (that is, it's usually the most noble, most admirable, most unsuspecting people that can have the most subtle attraction)! But in which relationships do I need to be careful? And how can I develop accountability in those relationships? Carelessness is one quality that we cannot afford to employ with our affections and our sexuality.