A lot of it is being convinced that if you try that bit harder, if you don't give them any reason to get upset with you, then things could get back to the nice way they were once upon a whenever. Sometimes it's thinking that if you take the abuse, you're protecting someone else from getting it. Or one person desperately wants to get away, but their child/sibling/parent/whoever is too terrified to leave the house because of what the abuser might do to them when he/she catches up with them. "I couldn't leave them there alone." Threats like "if you try and leave/don't come back, if you tell anyone, I will hunt you down and I will hurt you so badly this will seem like a day at the park, and then I'll start on your family" can be very effective. Not having any money of your own and thinking "well, (abuser) does this this and this, but their money pays for that that and that, can I subject my kids to a life on benefits?" There's more but I'll stop now.