You yourself should reprove yourself,
should examine yourself.
As a self-guarded monk
with guarded self,
mindful, you dwell at ease.

Your own self is
your own mainstay.
Your own self is
your own guide.
Therefore you should
watch over yourself–
as a trader, a fine steed.

-Dhammapada, 25, translated by Thanissaro Bhikkhu.