If you really want to become skillful in your thoughts, words, and deeds, you need a trustworthy friend to point out your blind spots. And because those spots are blindest around your unskillful habits, the primary duty of a trustworthy friend is to point out your faults—for only when you see your faults can you correct them; only when you correct them are you benefiting from your friend’s compassion in pointing them out.
– Thanissaro Bhikkhu, “The Power of Judgment”