When Yang-shan Hui-chi (807-883), as a young monk, paid a visit to the Ch'an master Hsing-k'ung, there was a monk who asked Hsing-k'ung:
-What is the meaning of the Patriarch's coming from the West?
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...)