The following passage is from 'Heart Advice, Weekly Quotes From Pema Chodron'.
TROUBLEMAKERS SHOW US WHERE WE'RE STUCK
"Those who give us a hard time, who are difficult to be around
or who constantly blow our cover,
are the very ones who show us where we were stuck.
The great meditation master Atisha always traveled with his
Bengali tea-boy because it kept him honest.
Without his ill-tempered servant to test him,
he might have been able to deceive himself
about his degree of equanimity.
Troublemakers up the ante:
if we can practice patience with them,
we can practice it with anyone."