cheaters will always cheat

Why do people say this? Why a former cheaters doomed as a cheater for life? I'm not proud, but I've cheated in 2 relationship before. I've had about 5 solid relanships. I've been married for the last 6 years and I'm not going to cheat on my husband. But why am doomed to be a cheater for life? Why can't cheaters change. I was in unhealthy relationships and I just didn't love the person like I thought so I cheated. I fucked up but I admit that. I'm deeply in love with husband so cheating will never be an option.