I Loved Someone That Didn't Love Me

Not a romantic type of love but has anyone ever been in a situation where you try so hard to have a relationship with someone and they treat you badly, then when you build yourself back up and are strong enough to walk away they always try to bring you right back? I never understood why these people Ive known since I was a child keep me hanging on when it’s obvious they don’t want me. Why do some people do that? Is it a power thing?