J, I read an article when I first found out about OW that really helped me. It's on Psychology Today and called "Once a Cheater, Always a Cheater... Maybe Not." You can Google it. It helped me realize how/why it could happen and made me stop blaming myself and comparing myself to the OW. It's a really great article analyzing the types of affairs, written by a psychologist who had an affair himself.
Comparisons between self and OP only add to more confusion, especially with MLC. It became clear to me that it was about the first willing person, and that person is going to have a lot of insecurities and low self respect, along with other issues to allow him/her be used that way. It helped to know that it had nothing to do with me. This quote from MWD has also helped me a lot too:
"I've met people whose spouses refused to have sex for years and although that made them miserable, they simply could not cheat. I've met other people who, when their relationships hit predictable bumps in the road, rather than work things out, they sought comfort in the arms of strangers. Unhappy marriages don't cause infidelity. Being unfaithful causes infidelity."
M38,H39 M:16Y BD:8/12 OWDB:11/12 S:11/12-5/13 "Temp" home:6/13 OW dropped:9/13 "I love you":12/13 H ring on:2/14 Depression back:5/15 "I'm done:" 7/15 H moved out: 3/16 H moved back: 12/16 Working on us: 3/17