A famous maggid (preacher) once visited Rabbi Chaim of Sanz. Rabbi Chaim complained to him that since he was a Rebbe, a leader, no one ever rebuked him for anything. He asked the maggid to please tell him where he could improve himself.
The maggid remarked that he was surprised that Rabbi Chaim's house did not have the requisite square cubit of unfinished wall space that one is to leave as a reminder of the ruin of the Temple. Rabbi Chaim promptly arose and scraped the paint off an area of the wall, deeply thanking the maggid for calling his attention to this delinquency.
We are often unable to see our own faults. Still, most people dislike rebuke. Even if they are not frankly offended by someone else pointing out their imperfections, they are rarely grateful for being reprimanded. Knowing that we might react defensively, people who note our mistakes and are in a position to rebuke us will be reluctant to provoke us. We should actively encourage them, as Rabbi Chaim did, for we can learn from their observations, eliminate our character defects, and thereby better ourselves.