I was wrong

I've long believed, and often said, that it is very rare for both parties to a failed relationship to be at fault. I now know that is wrong. I now think it's very rare to find a case where only one person is at fault.

Why was I fooled? Part of the reason was that I leaned heavily on the fact that certain facts about what someone has done are indisputable. We learn that, "X had an affair." Well, it's all her fault then!

My point here is not that people who have affairs do so because the relationship is going badly. That happens sometimes but other times people have affairs because their just selfish little shits. My point is that when the other person in a relationship unilaterally does things that are really crappy those facts can easily be manipulated into telling a very one-sided story. This story usually starts with an easy lie we tell ourselves (I did this once upon a time). It goes like this: "My biggest mistake was trusting you." That's what whiny little victims say.

To believe that you have to believe that there was some really big betrayal or a series of betrayals that came out of nowhere and caught you completely off guard. That seems possible or, rather, the first part and the last part seem possible. I can believe there was a huge betrayal or betrayals and I can believe these caught me completely off guard. What is a bit more of s stretch is the second part, that these "betrayals" came out of nowhere. To put it bluntly, "betrayal" is just "warning sign" writ very large.

Why did I not see this before?

•  For a long time I was a whiny little victim about bad treatment I'd received from women in my life, most notably from my mother.
• Every time I got into a relationship, or even just a good friendship, with a woman I told myself that I was incredibly fortunate. I spent too much time worrying that she might reject me and not nearly enough time asking if she was a safe bet.
• I knew that while everyone has faults, you can only control yourself, so I focused on working harder on myself when things got difficult. That sounds sane but is actually insane. I was a fixer. I had come to believe that a bad relationship can be fixed by one party unilaterally deciding to work harder at it. 
• I didn't ask the hard question. One reasonable safety check to apply to a relationship not only at the beginning but all along is to ask yourself whether the other person really wants you. That is a different question from do they really want to be in a relationship. Most people (desperately) want to be in a relationship. But do they want you just as you are?