Do breakups always hurt?

Say you’re already interested in someone new, but you’re so afraid to part from the one you know. Is that always the case or does this mean I should hang on? he’s toxic... but I don’t want to let go for some reason, should I still knowing it might be best? This other guy is a catch, and I’d hate to miss out on him for someone who’s broken my heart more than once. Yet I can’t push myself, why!?