The part where someone screws up is when someone else becomes a source of your happiness and your pain. Some days you can be on top of the world and other days you don't want to come out of your room. The worst part is, on both days you go to them. They give you happiness so you tell them about all the things that happened in your day. they give you pain so you try to look for comfort in them hoping they'll say something to make you feel better but they're also the the ones who made you feel pain in the first place so you're literally looking for happiness the same place you lost it... and it doesn't always work. So you're stuck with pain until you find a way to make yourself feel better or you do find it in that person. If you do that's still very toxic cause you'd be going into a cycle. But you feel that just having that person in your life is enough so you decide to go through the cycle each time.