From: 'The Wisdom of No Escape'
Impermanence means that the essence of life is fleeting. Some people are so skillful at their mindfulness practice that they can actually see each and every little movement of mind-changing, changing, changing. They can also feel body changing, changing, changing. It's absolutely amazing. The heart pumps blood all the time and the blood keeps going and the food gets digested and the whole thing happens. It's amazing and it's very impermanent. Every time you travel in a car, that might be the end. If you get really paranoid, impermanence can drive you crazy because you're scared to step off the curb, you're scared to go out of your house. You realize how dangerous life is. It's good to realize how dangerous it is because that makes the sense of impermanence real. It is good to realize that you will die, that death is right there on your shoulder all the time. Many religions have meditations on death to let it penetrate our thick skulls that life doesn't last forever. It might be over in the next instant! Sometimes it's said that the end of every out-breath is actually the end; the opportunity is there to die completely. Suzuki Roshi gave the instructions, "Sit still. Don't anticipate. Just be willing to die over and over again." Let that be a reminder. Being willing to die over and over again heightens the first reminder, the sense of gratitude and preciousness. Impermanence can teach you a lot about how to cheer up. Sometimes let it scare you. It is said, "Practice as if your hair were on fire."
~Pema Chodron