Bruce has always known that being in a relationship would be no good for the person he loves, he is Batman, a vigilante, criminals would use anything and anyone against him, but still he was stubborn enough to decide to give you his heart, to start a relationship, to love you.

He should've known that you would get hurt sooner or later, he just was too blinded by love to think rationally, he thought he would be able to protect you, to make sure no one would hurt you, but that didn't seem like the case.

Ra's al Ghul as kidnapped you threatening to hurt you if he didn't join the Leauge of Assassins. He managed to take you back and bring you to the Wayne's Manor without a scratch. Ra's al Ghul managed to make him doubt himself:what if you got hurt?, what if he was too late?, what if it happens again and next time he won't be able to save you. With these thoughts he decided that it would be best for you to break up, to be with someone normal, someone who isn't a vigilante, someone who doesn't put you in danger.

"We should break up" He says, you were eating in the dining room of the Manor, Alfred was in another room to give you privacy, he tried to convince Bruce to not do this, to not end a relationship as good as yours, but he was stubborn. The room was quiet until he spoke again "I'll call a moving company. I've cleaned the guest room so you can sleep there for now, until you find a place to stay"