The goal of Zen practice is to regain and keep our beginner's mind, the mind we are born with. That is all. There is no need to have a deep understanding of Zen.
Our expert mind tends to be judgemental and dualistic; "this is good, that is bad". It entertains self-centered thoughts of achievement; "I have done this, and soon I will do that". These thoughts of longing make our mind demanding; we feel discontent, and forever focused on what happens next. We are able to appreciate moments only in anticipation - "when I retire", "when I buy that new something"; or after they are gone - "those were good times".
Our original mind, on the other hand, is rich, empty, and ready; it is open to everything. In the beginner's mind, there is no thought, "I have attained something" or "I am going to attain that". When we have no thoughts of achievement or longing, then our mind is self-sufficient, and unrestricted. We are true to ourselves, compassionate, and in sympathy with all beings. We delight in the miracle of existence, and find contentment in everyday activity, unburdened by thoughts of the end result.
As long as we are alive, we are doing something. We eat, we sleep, we walk, we cook. Sometimes, the activity takes effort; we write a report, prepare for a test, or go to the dentist. Activity is part of what we are, it is an expression of our nature. But if you do something in order to gain something, then you are not really doing it. If you say "I will drive faster so that I get there quicker", then you are not really driving. Or if you say "I want to do this well, so that it would look beautiful", then your activity is burdened by the judgement afterwards.
The thought of gaining something keeps us from the calmness that activity brings. It is the activity that expresses our nature, not the end result it brings. When you give up, when you no longer do an activity in order to achieve something, then you achieve calmness in activity. Then you are really doing something. Your true nature is being expressed, and your innermost being is appeased.
When ants work, they work. That is all. One step at a time. They do not think "I am almost done", or "that other ant is slacking off" or "we need to do a good job". There is no thought of time or progress. Their minds stop, and they bask in the honest, sincere activity of the moment.
So when you eat, just eat. Do not read a magazine, or think "I need to do something after lunch". Stop your mind. Right now, you are eating. Look at your food, smell the aroma, taste the flavor, feel the texture. After eating, you will be drinking water. Give it the same attention. And after that, you will be doing something else.
When you walk, just walk. If you walk in order to get somewhere, then you are not really walking. You should expect to make progress little by little, or even no progress at all; just be sincere to the activity and make full effort in each moment.
We often hear ``Things were so good. Why couldn't it have lasted forever?"
Transiency or change is a basic teaching of Buddhism. Nothing lasts forever. We are alive right now, but in time that will change. Our jobs are at best transient. Our health changes. Our families change; soon the children will be grown and gone. Things even change from minute to minute. You are full now, but will be hungry later. Or sleepy, or happy.
When we realize the everlasting truth of "Everything changes", and we find our composure in it, we find ourselves in Nirvana. Without accepting the fact that everything changes, we cannot find perfect composure. Unfortunately, this truth is difficult for us to accept, which causes much of our suffering.
We should find perfect existence through imperfect existence. We cannot always be happy, we will sometimes be sad. Happy is good, but sad is also good.
Pleasure is not different from difficulty. Good is not different from bad. Bad is good; good is bad. They are two sides of one coin. We know we will experience both pleasure and difficulty. If you try to escape difficulty, your effort will be in vain. With the acceptance of the fact that everything changes, we can find pleasure in difficulty. This is the basic teaching of how to live in this world.
You have to make the effort. Sometimes it is not so difficult, sometimes it is more difficult. That is okay. The important thing is to make the effort; accept that things change, and find perfection in imperfect existence.