Man, this is a great topic! Basically I regret believing that Mom had everything right...especially while I was thinking "that can't be right".
Biggest regret: I married three times; #1 for all we had in common, #2 for money, and #3 for security. And I divorced three times; #1 because one of the things we had in common was that we were both attracted to men, #2 physical abuse, #3 he had a severe gambling addiction (wiped out my savings).
The thing is, Mom told my sisters and I that marriage was something we
had to do, that a woman who didn't marry had something wrong with her, would grow old friendless, shunned, alienated from society. I knew in my heart that I didn't want to get married. I only did it because Mom started suspecting I was gay. In her words exactly, "I'd rather be told my child has cancer than to be told she's gay!" Incredible, right?
The 2nd marriage (for money) was particularly for her sake, because "Of course [your first marriage] didn't work! You marry for money, not for what you have in common...women have
nothing in common with men!"

layful: pfff!
If I hadn't bought into Mom's garbage, I'd have had an infinitely smoother, happier life.