We might think, “It is right; I have to practice Dharma in this lifetime because human life is precious and hard to obtain. But first I should make some money, travel, wait until my children grow up, or wait until another day for whatever reason.” Of this the Buddha said that life is impermanent. It is as impermanent as the clouds of autumn; they appear in the sky one moment and disappear the next.
There is a very beautiful parable by Gongthang Tempe Drönme. One day a man fell off a cliff. Halfway down the steep, rocky slope there was a tuft of grass growing, which the man was able to grasp to stop his fall. He hung onto the grass with all his might, for if he were to let go, he would die.
Then, as he clung to it, a white mouse came and started to nibble on a bit of the grass. Later, a black mouse arrived and ate a bit more of the grass. Gradually, the mice kept nibbling at the grass that the man was clutching—first the white mouse, then the black, then the white again—until finally, when one of the mice gnawed through the last blade of grass, the man slipped off the rock and fell down the cliff to his death.
In this parable, the white mouse represents day, the black one night. The man is really dying from the beginning and is just temporarily hanging on. Day comes and exhausts itself; then night comes and exhausts itself. Then, at last, death arrives.
In the same way, we too are just waiting or hanging on until death comes, since that is our ultimate destiny. We are here not to live, but to die. But even so, we do not really think or care about it.
Like a shooting arrow, the speed of life is moving very fast toward its target, which is death. We do not even realize this truth. While it is not obvious that there are such things as karma, rebirth, and realization because we cannot readily see or know them, the certainty of death is right in front of our eyes, yet it is still shocking for us to realize it.
The Buddha said:
The three worlds are impermanent, like the clouds of autumn.
The births and deaths of beings are like watching a dance.
The speed of human lives is like lightning in the sky.
It passes swiftly as a stream down a steep mountain.
If we watch a dance, first we can see the dancers’ faces, next their backs, and then their faces again. In the same way, today we die, tomorrow we take rebirth, and the next day we die again.
Our lives are moving so fast that we are not able to postpone even a single moment as we go straight from birth to death, without realizing it.
If we think we will wait until tomorrow to practice we are fooling ourselves, since we are just hanging on a cliff. So we must start our practice today, and not even today, but right now.
(Source: Thondup, Tulku. Enlightened Journey: Buddhist Practice as Daily Life. Shambhala. Kindle Edition.)