Be brave enough to change relationships and situations that aren't working

I can tend to get into relationships or situations that just don’t work. When I get in a situation it takes me a long time even after I relize it is wrong to get out of it. Now the relationships I get into that don’t work are real hard for me to get out of. I keep buying that “one more chance and I’ll change” excuse. After about a week of being broken up I end up getting back in. It usually goes like that untill I reach a breaking point and end up flipping out on the guy.