One day, Chang-sha Ching-tsen (d. 868), one of the well-known Chinese Ch'an masters, wandered in the mountain. When he was back just at the gate of the temple, the head monk asked him:
-Where have you been, Sir?
Sometimes I am confused whether I am thinking thoughts, or whether thoughts enter from elsewhere. Because it is impossible to think a thought and recognize you are the thinker while you are thinking the thought.
Try to be aware of a your mind and at the same time try to recite something in your head. It doesn't work. At best it is an on-off switch (thought-thinker-thought-thinker...)