If you don't know you don't know, you think you know.
Many mistakes are made by people who think they know more than they do. It's important to know the limits of your knowledge. As Dirty Harry said, "A man's got to know his limitations." Not knowing you don't know may be even worse than not knowing you know.

If you don't know you know, you think you don't know.
Like lack of self confidence, lack of self-knowledge can be a great hindrance to accomplishment. If you think you don't know how to do something, you probably won't try to do it.

If you know you don't know, you don't think you know.
Yes, but are you sure you know you don't know?

If you know you know, you don't think you don't know.
The way it should be. You know, and you know you know. So you can do.