FWW here. For me, it was getting caught and seeing what the results of my actions actual were (husband nearly left me, and still isn't 100% he's not going to, losing my kids part of the time, nearly losing my job, etc.). It was enough to snap me out of the fog and break the addiction in one quick swoop.
From what I read though, even when the WS leaves for the AP, that relationship tends to unravel fairly quickly, since once the realities of day-to-day life are applied, the affair is much less enjoyable and exciting. During the A, you don't have to deal with regular stressors, such as paying bills, getting along, regular stuff that a couple has to handle. It's all fun and excitement and surreal. Take away those elements, and you're left with a relationship that will need actual work, plus you have the added bonus of knowing you both cheated, so now you have to be concerned about whether each of you will cheat on each other.
