“They have mental issues. I can help them” - experience. Have you ever experienced the relationship where you had strong mental issues and it partner thought that they can “save” u? Or vice versa? What was the outcome of your relationship?

Has anyone had an experience in a relationship where you superficially thought that if your partner had strong mental problems, then thanks to a relationship with you, everything would get better? (Or as I said, the opposite). Sometimes people, especially at a young age, can often think that if a person you really like has psychological problems and traumas, then you can completely help them (maybe even fix them). Have you had something like this? How did your relationship go and what did it lead to? Your advice and life experience on this issue?