How do we spend time when sitting? As the state of sitting, what becomes a problem is prudence and discretion, various things come up to mind or occur, or there is the case that we deliberately think from this side; the side of self. In general, those are thoughts. While being in zazen, you should not deal with such sort of things. You should not distinguish the thoughts that come up with your own views. You ought not to judge so called goods or wrongs. It means that you should not do things like this is good, this is wrong, or this is right, this is mistaken.
To be more specific, when various things come out on sitting, for the human beings, there are things which weigh on their mind. Being so you usually start doing things in your head to try to solve the problem that is bothering you. You should not do this anyway. Therefore, whatever entered into your mind, if there are things weigh on your mind among what you recalled or you thought, you do not spend your time dealing with them or trying to do something about them. And you don't do anything to stop it from coming out. You just sit without making up things or without making any alternations from this side. That is the way of practice when doing zazen, which is called Kufuu; ingenuity.
As we sit here like this, we can hear the sound of cars. Even if we don’t want to hear, when the sound of cars happens, it can be heard “buzz-buzz.” We don’t do ourselves “to listen” intentionally. It is not like we do not to hear. When we stay doing nothing, when sounding, we are always in the state as it is, we are formed as such. That is expressed “Give up the operation of Shinisiki (sensation, discrimination and recognition)” “Stop measuring with Nensokan (consciousness, thoughts, views)” In a word, you don’t take on or deal with what comes out by the way of thinking. It's the same thing, but it's about learning by the way of not-thinking which is called "non-thinking," (In general, "learning" refers to using the way of thinking to understand an object, but here, as mentioned above, it refers to being a "buzz-buzz" when there is a "buzz-buzz.”) To put it a little differently, I would say that we stay that we don’t really use various things that we acquired after we were born. As the state one is born. That way we can get in touch with the essence of human beings. So that is how we should practice. Those are the important ways spending time in zazen.
The reason why it is so difficult for people to accept this recommendation is that it is what bothers them and a problem they face, though, it is okay to leave it alone without addressing it, they are half in doubt. Normally, they would take up the things that are bothering them, the things that are causing them problems, and try to solve them. But if you do that, it's not zazen.
The main reason why we should leave it alone is to see through what the truth of the matter is, how the way of things really is. If you insert any human thought or view into what you touch, you are distorting the facts, which is the first thing. That is why we should not treat with human views or the way of thinking at all. In this way, the truth of matter and facts are conveyed as they are. That’s what I would like you to do. 
The other is that what we say we are troubled or suffering or having a problem with is a phenomenon that occurs on the basis of our thoughts. Being so I want you experience what happens to us when we don’t use the way of thinking. In fact, we can go on living without dealing with it and there is no problem. Once something which weighs on your mind appears, however, you are usually convinced that it cannot be settled without making it go away somehow. Well, that's what I'm going to say in theory.
So, what happens when you don't take up such things at all, when they appear, they just move and work. You never be thinking continuously. Thoughts cease instantly when they appear. Thoughts come and go. It's made to disappear even when you don't touch it yourself. You'll see what I mean when you try it.
 And in the beginning you should be especially careful not to fall into sleep. To stay awake, “Eyes should always remain open,” sit with eyes open. If you come to close your eyes, you will definitely be pulled around by the thoughts and the things that come up. By the way when closing eyes, if you can see something there, it is the trick of your imagination and you are dealing with what you think in the head. It cannot be zazen at all anymore from the beginning. So, keep your eyes open. When you keep your eyes open, you should be able to see exactly what is in front of you. Because you can clarify the difference between what’s in front of you and what you’re picturing in your head, I want you just to be the state of now what’s in front of you, without dealing with what you are picturing in your head.
And then there are all the other functions of the body, such as the ears, which are all intact. When we sit like this, as each of them is functioning, even if you don’t do anything yourself, they are functioning variously touching on conditions. Try to stay with just that.
Well please do as such carefully. Anyway, please try to practice. After this there will be time for you to talk to me in private, Dokusan; private consultation, so please feel free to be frank. 
I would like to reiterate that “sitting” is not about dealing with the way of thinking, things that come up. It's that you don’t do that.