What does it mean when you care about someone, deeply, and you don't know why?

Anonymous
This person has repeatedly hurt you, and they even rejected you before but you still want them. You want them to be happy and you would do anything to see them smile and you care about them unconditionally. You would possibly even sacrifice yourself to make sure they're okay. You know you shouldn't want them so much and you've NEVER felt this way about another person. You care about them so much that it hurts you LITERALLY. You feel dumb for still caring about them even though they treated you like scum but you can't stop having these feelings for them. You feel like if they were to ever give you a chance that you could be so perfect together. You feel like you are perfect for them even though they don't realize it.

What does this mean? Why do you care about them so much? Why can't you stop caring about them?
What does it mean when you care about someone, deeply, and you don't know why?
2 Opinion