An adult with a mental disability tries to raise his daughter alone

This movie is about a man who has a (physical/mental?) disability, and is the father of a small daughter, which he tries to raise by himself, but the (state) authorities try to take her from him, considering he’s not fit to take care of her.
I was positive that this is a movie with Billy Bob Thornton. But I went through his movies, and I couldn’t find it.
I think that in the end he gets the change to raise his daughter, after battling for that right.
This is all I recall of it, sorry for not being able to offer more information.