Concentration is not to try hard to watch something. In zazen if you try to look at one spot you will be tired in about five minutes. This is not concentration. Concentration means freedom. So your effort should be directed at nothing. You should concentrate on nothing.
We were parted long ago, yet we have never been separated even for a moment. We are facing each other all day long, yet we have never met.
I raise my hand; I take a book from the other side of the desk; I hear boys playing ball outside my window; I see the clouds blown away beyond the neighboring woods - in all these I am practicing Zen, I am living Zen. No worldly discussion is necessary, nor any explanation.
The Zen "genius" sleeps in every one of us and demands an awakening.
Childlikeness' has to be restored with long years of training in the art of self-forgetfulness.