I’m not sure if I want to have it or not. Tolkien doesn’t have a strict routine with it, though I believe he does have some commentary on things. Rowling also uses inner dialogue.
It seems that you can do a better job showing the progression of learning and feeling in the protagonist if you show not just how he or she acts but also how he or she thinks and feels. It’s a strength of writing that you can do this. It seems like it’d be a more fertile soil for showing the changes in the character, which is what the story is all about, really.