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 we’re stuck. The great meditation master Atisha always traveled with his belligerent 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.
From No Time to Lose: A Timely Guide to the Way of the Bodhisattva by Pema Chödrön, page 210