Running

Somedays, you struggle to run even two kilometers. Your breath is fine, no muscles are hurting, but you just cannot bring yourself put one foot in-front of the other, and to keep doing it.
The very next day, you are in the groove. You ignore the sharp pang of pain in your knee, the eyes nearly closing with sleep. The only thing that can stop you is the clock.
It is not the legs or the lungs that determine how far or how fast you can run. It is the heart, and only the heart.
Isn't Life like that too?

Drabble (n) - an extremely short work exactly one hundred words in length. The purpose of the drabble is brevity and to test the author's ability to express interesting and meaningful ideas in an extremely confined space.