This topic was suggested by Joel (pronounced Joe-Elle) Mayorga. I’m going to assuming he’s talking about relationship partners.
I can’t really answer this question in much detail because I haven’t found the right one. And I think it’s different for everyone anyway.
But I was told once by a very good friend that you know you are right for a person if you can tolerate a person even when only the darkside of their character is showing. It seems wise enough, as long as that person’s darkside isn’t putting you in physical danger.