In not always so (on p. 50-2 of my copy):
Our everyday life is like a movie playing on the wide screen. Most people are interested in the picture on the screen without realizing there is a screen. When the movie stops and you don't see anything anymore, you think, "I must come again tomorrow evening ... I will come back and see another show." When you are just interested in the movie on the screen and it ends, then you expect another show tomorrow, or maybe you are discouraged because there is nothing good on right now. You don't realize the screen is always there.
But when you are practicing, you realize that your mind is like a screen. If the screen is colorful, colorful enough to attract people, then it will not serve its purpose. So to have a screen which is not colorful – to have a pure, plain white screen – is the most important point. But most people are not interested in the pure white screen.
I think it is good to be excited by seeing a movie. To some extent, you can enjoy the movie because you know that it is a movie. Even though you have no idea of the screen, still your interest is based on an understanding that this is a movie with a screen and there is a projector or something artificial. So you can enjoy it. That is how we enjoy our life. If you have no idea of the screen or the projector, perhaps you cannot see it as a movie.
Zazen practice is necessary to know the kind of screen you have and to enjoy your life as you enjoy movies in the theater. You are not afraid of the screen. You do not have any particular feeling for the screen, which is just a white screen. So you are not afraid of your life at all. You enjoy something you are afraid of. You enjoy something that makes you angry or makes you cry, and you enjoy the crying and the anger too.
If you have no idea of the screen, then you will even be afraid of enlightenment: "What is it?" "Oh, my!" If someone attains enlightenment, you may ask him about the experience that he had. When you hear about the experience, you may say, "Oh, no! That is not for me." But it is just a movie you know, something for you to enjoy. And if you want to enjoy the movie you should know that it is the combination of film and light and screen, and that the most important thing is the plain white screen.
That white screen is not something you can actually attain; it is something you always have. The reason you don't feel you have it is because your mind is too busy. Once in a while you should stop all your activities and make your screen white. That is zazen. That is the foundation of our everyday life and our meditation practice. Without this kind of foundation your practice will not work. All the instructions you receive are about how to have a clean white screen, even though it is never pure white because of various attachments and previous stains.