Walking is Zen; sitting, too.
Great Faith, Great Courage, Great Doubt
You must decide to practice and very strongly keep this decision. This requires great faith, great courage, and great questioning.
What is great faith? Great faith means that at all times you keep the mind which decided to practice no matter what. It is like a hen sitting on her eggs. She sits on them constantly, caring for them and giving them warmth, so that they will hatch. If she becomes careless or negligent the eggs will not hatch and will not become chicks. So Zen mind means always and everywhere believing in myself. I vow to become Buddha and save all people.
Next, what is great courage? This means bringing all your energy to one point. It is like a cat hunting a mouse. The mouse has retreated into its hole, but the cat waits outside the hole for hours on end without the slightest movement. It is totally concentrated on the mouse hole. This is Zen mind cutting off all thinking and directing all your energy to one point.
Next, great questioning. This is like a child who thinks only of its mother, or a man dying of thirst who thinks only of water. It is called one mind. If you question with great sincerity, there will only be don’t know mind.
If you keep these three, great faith, great courage, and great questioning, you will soon attain enlightenment.