Once you have located your own breath point with clarity, don’t deviate from
that spot. Use this single point in order to keep your attention fixed.
Without having selected such a point, you will find yourself moving in and
out of the nose, going up and down the windpipe, eternally chasing after the
breath which you can never catch because it keeps changing, moving and
flowing. If you ever sawed wood you already know the trick. As a carpenter,
you don’t stand there watching the saw blade going up and down. You would
get dizzy. You fix your eyes on the spot where the teeth of the blade dig
into the wood. It is the only way you can saw a straight line. As a
meditator, you focus your attention on that single spot of sensation inside
the nose. From this vantage point, you watch the entire movement of breath
with clear and collected attention.
– Henepola Gunaratana, Mindfulness in Plain English from Everyday Mind, a Tricycle book edited by Jean Smith