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.
She was an alcoholic with border-line personality disorder, and as a naive and lonely young Scotsman I foolishly mistook her for a bright girl with a quirky personality who liked a drink and had occasional violent moodswings. Took way too long to realise what the gravity of her condition meant. I was emotionally inexperienced and trusting. And I paid the price.
On the bright side, when i came out of that relationship and healed I met someone well-balanced and kind, who is now my wife. I’m so grateful for the love i now have and the relative stability of my life, and in a weird way I’m glad I went through what I did with my ex, as it makes me appreciate what I now have.