I’ll start.
We had great chemistry but different goals. She was religious and looking to marry and thought she could change me, a non-religious person who intends to remain unmarried and childless. I was up front about the lack of religion and the lack of desire for marriage. She was not up front about her intent to change me.
After two months of regular flings she told me we couldn’t see each other anymore, because she wanted someone to go to church with, it was my fault she was living a sinful life (totally), and she was cheating on me with another dude was a Christian.
The last two relationships I was in failed because I simply could not give them the attention and love they deserved. Which is entirely my fault. My wife liked both of them, and we’re all still in communicaton, but it’s hard to give people the love they deserve and need.