We believe we begin to think when we start to reflect on an object or concept; but in fact, when we start to do this we just say to ourselves what we already know, or let's say potentially know, and this potential knowledge is a real mystery.
So in the end, being exhausted by thinking, we have to interrupt our thoughts and return to reality to re-charge the potential. The real mystery, therefore, occurs when we interrupt our thoughts (that's why the word 'intellectual' for me is rather dirty.)