Emptiness
When you study Buddhism you should have a general house cleaning in your mind.
If you want to understand Buddhism it is necessary for you to forget all about your preconceived ideas.
The Buddhist understanding of life includes both existence and non-existence. The bird both exists and does not exist at the same time.
We say true existence comes from emptiness and goes back again into emptiness.
As long as we have some definite idea about or some home in the future, we cannot really be serious with the moment that exists right now.
When you understand one thing through and through, you understand everything. When you try to understand everything, you will not understand anything. The best way is to understand yourself, and then you will understand everything. So when you try hard to make your own way, you will help others, and you will be helped by others. Before you make your own way you cannot help anyone, and no one can help you.
But before you put something in your room, it is necessary for you to take out something.
But as long as you have some fixed idea or are caught by some habitual way of doing things, you cannot appreciate things in their true sense.
If you seek for freedom, you cannot find it. Absolute freedom itself is necessary before you can acquire absolute freedom.
To go one mile to the west means to go back one mile to the east.
As long as you are caught by duality you cannot attain absolute freedom, and you cannot concentrate.
Concentration means freedom. So your effort should be directed at nothing. You should be concentrated on nothing. In zazen practice we say your mind should be concentrate on your breathing, but the way to keep your mind on your breathing is to forget all about yourself and just to sit and feel your breathing. If you are concentrated on your breathing you will forget yourself, and if you forget yourself you will be concentrated on your breathing.