People with BPD are really good at playing chameleon. Their own emotional state is kind of like a mirror of what you feel. They can adopt the mannerisms and interests of people around them. And so this idealization demonization aspect is really hard to deal with because on one day, your God's gift to this person and you fix everything in their life. On the other day, they get angry with you because you're starting to pull away with them and they treat you like absolute crap. So how do you succeed? The first thing is don't give up.