What is the self?
Generally one thinks of the self as "I' or "Me", something that relates to the outside world. But in fact, you may be surprise to find that the self is just the self. An accumulation of attention.
It's like a man/woman who is focused on the sound of a cricket that they forget the sound of the air conditioner. It's just a focus of attention. When you focus your attention on something, that thing becomes a "thing". However, it is not that.
Our common practice is to focus on thoughts. This is habit or "what we are used to. Perhaps we have a pain, or a shaking feeling, or a whatever. Our tendency is to focus on that and in doing so, our attention gets held up. It is not "one" thing. It is just things. When tired sleep, when hungry eat. When typing, type, when drowsy, drowse. Pay attention. What does pay attention mean to our practice? It means discovering the self, the accumulation. It is just being here. Nothing to get. No one to see. No bills to pay, just the paying of them. No time to sit, just sitting time.
Sit up straight. Pay attention. What happens when you do that? What happens to whatever it was that we were so worried about a moment ago? Don't try to get something, or gain something. That's just more of the same. Don't try to be calm, or solve your problems. Sit up straight, but don't try too hard. Open up. These are the things we learn. We learn this through Zazen.
Tie your shoes. Don't Tie your shoes and think about what is going to happen at the office. Just tie them.Drink your drink. Don't think about what you have to do "after" you drink your drink. Just drink.
Study the self. See the focus, and how things arise. Don't get caught up in it, and come back to paying attention and sitting Zazen.