Adapted from a recent online discussion.
On those who judge their partners in one-night stands but absolve themselves:
Your reader's belief that her one-night stand was caused by "a series of fluke circumstances" while judging "how easy it was for the other person to jump into bed" reflects such a common asymmetry in perspective that psychologists call it the "fundamental attribution error." People generally attribute their own behavior to the complex interplay of situational forces ("I was swept up by the wine, the moonlight, our mutual interest in the Washington Post") whereas they attribute the behavior of other people to simple internal dispositions (they are "easy," or "a slut").
Often people can see how different situations cause them to act differently ("I know myself, and I know the one-night stand resulted from …"), but they cannot see such situational impact in other people. Sometimes it can help to suggest that they adopt the perspective of the other person.
On women who, around 40, become "invisible" to men:
I have a vague memory of contemplating this idea as a divorced mother in my mid-30s with no success at finding "the one"; there was a time when I longed for a second opinion.
Now, I gleefully make my own choices — good or bad. I love my solitude. I love not feeling guilty about leaving dishes in the sink, or watching a movie instead of vacuuming the cat hair. I love being able to have a house that is as quiet as I want it — no sports on TV, no jazz Sundays, or power-tool weekends — unless I want it. I love not having to acquiesce to entertaining his friends or sharing in his favorite activity. I moved to the city so that I would have a multitude of friendly neighbors willing to help me out in a pinch.
Loving all of these things, I have no desire to be romantically involved with any man and therefore do not care whether I'm visible. This feeling is very freeing and I love it. I hope it's not just a phase.
On ethical nonmonogamy:
Earlier this year, while working at my father's business, I discovered his affairs. My mother, his wife of 20-plus years, is a psychologically unstable narcissist who makes life hell for anyone who has anything to do with her.
I knew he stayed in this miserable marriage for the kids, and I knew she was too self-absorbed to ever be there for him the way a wife should, yet I felt like he was betraying our family.
However, since my discovery, I have noticed that he has become more down on himself than ever. I now feel bad for being judgmental and realize how lonely he must have been all those years while he was providing the only stability we ever had. Obviously I am not a mind reader, but I think that, more than sex, he wants a loving partner, which my mom has never been and never will be. He is in his 60s and has probably realized that his prospects for ever having a supportive, loving relationship are dim.
I don't really know what my father should do, but people need to understand that using sex to paper over deep emotional problems never works out.