When you hit the nail on the head, you say or do something perfectly right, or you figure something out that’s been bothering you or people around you. You might hear this idiom when someone is agreeing with someone else, or congratulating them for coming to a valid conclusion. It can also be used to precisely describe the cause of a problem or situation, or when making a wonderful decision. This idiom is commonly heard in both social and professional situations.
I couldn’t have said it better myself. You really hit the nail on the head.
Some people change their ways, especially after receiving a disciplinary, but you hit the nail on the head with that employee. You knew he’d never change.