I think what other people have said rings true, only if the person genuinely wants to. If they're only going through the motions to make someone stay, and not truly wanting to change, they're not going to. But how do we know, right?
I don't think my ex will change, he is a narcissist, and could never love anyone like he does himself. Every problem we have is in my imagination, or normal behavior (to him). He went to anger management, but left after 3 sessions, then cancelled our couples counseling once I told him I knew he was trying to convince everyone I had pnd (she was a specialist in pnd, but did effective parenting post separation counseling too, so I still wanted to go).
Now he can't control me, or the situation with his lies, he is losing it. I really can't see him ever changing, but I would never really know as all he did was lie.
And the eggshell feeling is awful isn't it? I may not like being separated, but having a constant knot of fear and anxiety in my stomach is an awful feeling, and I'm glad that's gone.