We know because we are good students. We've studied hard and well. We are not fooled like we used to be. Still, our understanding doesn't pay the mortage, so to speak. Forgivness pays the mortage.
Forgiveness gets more necessary the more understanding we have. Irony! You may have noticed that I (and you) find myself facing unadulterated MURDEROUS rage....the kind that inspired the "Twinkie defense" and 9/10ths of what the world regards as "news" more often than I wish. Yes, "after all these years" on the spiritual journey, I sometimes mutter with a proverbial sigh. It seems like I'm beside myself with strong feelings of various forms of, shall we say, unpleasantness, every other day or so.
And in between these states, I experience more states of Peace.