It is quite an empowering phrase. When you really let it sink in, you begin to realize that no one can give you a grade, but yourself. (And I don’t mean this in the "all kids are special and everyone tries so it is not fair to give some kids As and Fs and lower their self esteem" kind of way.)
I mean this in the sense that it doesn’t matter if you got straight As and a perfect 4.0 GPA in college, you ultimately have to decide if you learned something, or if you just did the work.
It is only when you take ownership for the learning process and its result that you actually are able to accomplish the true goal of learning, which is the ability to put knowledge into action.