The only reason we can get upset with another person is because they remind us of something distasteful in ourselves.
While we might not actually do the things they are doing, their actions (and more importantly, the meaning we give their actions) stir something that resonates in us. Something we aren’t particularly fond of looking at within ourselves.
One of the early lessons in A Course in Miracles reads “I am never upset for the reason I think.” We think we are upset because of this other person. But this “difficult” person is simply reflecting back to us some obstacle we’ve erected that blocks against peace. And rather than viewing those barriers in us, we choose instead to dwell on their faults.
However, seen another way, our brother shifts from being the “difficult” person to becoming our “insightful teacher” who is showing us exactly where we need to look within. Consider this line from the Course: “Your brother is the mirror in which you see the image of yourself as long as perception lasts.”
So, whenever we find ourselves not at peace, consider what images our brother’s mirror is reflecting back to us. And with each of those images, ask to see it through the loving eyes of the Holy Spirit.