This takes great discipline. For the mind is unruly. It wants to charge ahead. It wallows in past mistakes and hurts. It can experience everything but the present moment. It oscillates between these two illusory states. For you cannot put your finger on the past and you cannot capture the future. They don’t really exist.
The zen person knows, and experiences first hand, what it feels like to be in the deep peace of the Present. It cannot be described but you can feel who has attained this state. They do not drag anything into the present that is not essential. They take out the mental garbage and stay clean.