Most of us know the value of a CP/Beta reader. (I think mine worth their weight in gold). They can point out those areas of a WIP that just don't quite work. Sometimes they can see your characters better than you can, and show you where you've let a character do something they wouldn't. They're great for brainstorming with when you get stuck, too.
Another place you need to listen is when they tell you to read a specific book or author as they think you can learn something from them. My CP Tammy did that this past week. She recommended a book to me. So I bought it and read it (and then I read the sequel). And as I read them, I saw what she was trying to tell me I needed in my current WIP.
I was making it too easy for my MC to accept that the male MC loved her. There needed to be more doubt, he needed to work for it more.
So. when your CP's/Beta's give you feedback, really listen. It can make all the difference in the world.