Some people practice throughout their entire lives just by paying attention to breathing. Everything that is true about anything is true about breath: its impermanent; it arises and it passes away. Yet if you didn't breath, you would become uncomfortable, so then you would take in a big inhalation and feel comfortable again. But if you hold onto the breath, its no longer comfortable, so you have to breathe out again. All the time shifting, shifting. Uncomfortableness is continually arising. We see everything keeps changing.
-Sylvia Boorstein, Tricycle: The Buddhist Review, Vol. 2, #1