I had an ex who had a couple planets in my 12th house. It’s crazy how accurate synastry overlays have turned out for me. For instance his Venus fell in my 12th house: “If your Venus is in your partner’s 12th house of a synastry overlay, you find yourself deeply moved in strange ways by the house person. For example, you may not be a needy person, but you find yourself being very needy or vulnerable around the house person. The house person may feel that you put out some “false advertising.” You (the Venus person) were one type of person when they met you, but in this relationship you act somewhat different. The house person can’t really understand certain aspects about you. They may feel that you are a dream come true, but at the same time, they’re not sure that this dream will last. It’s the 12th house overlay affecting both of you. Something about this overlay makes you feel insecure, as if the relationship is going to end but you don’t know why. The Venus person tries to hold on to the relationship, which confuses the house person even more. The house person doesn’t know if you want to continue or end the relationship. There’s an ephemeral quality to this overlay, so enjoy this mystical union while you have it. Now you see it, soon you may not.” Every. single. bit. of. it. held true.
It came to the point where I had to control myself from looking up synastries and charts of people I was romantically involved with until our relationship ended because they can feel so fatalistic.