Even after being behaved like very dirt for years, why some people still unable to leave their abusive life partners?

Why people cannot leave from their abusive partner?
Breaking-up with a person you are in too love with is easier said than be done. But why do people still hesitate to break their ties with someone who behaves them like dirtly? Whether we believe it or not, people still put up with their abusive partners for verious cause only they know. No matter how much counselling they take or decide to leave that partner, some kind of unexplainable power (or the lack of it) builds them retreat their steps. Here are the stories of a few people who could not leave from their abusive partners despite their maximum efforts.