There are many things in life which we remember and hold close to our hearts, whether it is an act of kindness or a grudge against someone else. Over time, the burden gets heavier and the bitterness grows stronger. However, the other party may not even remember what happened, and this creates a distinct disparity of experience between the two parties who are involved in the same incident. This Zen Buddhism koan is a great example to illustrate the burden of our minds.
Two monks were at a river crossing when they saw a young lady standing helplessly by the broken bridge, unable to get across. She requested the monks for help, and the younger monk refused outright. The elder monk kneeled down and carried the young woman across the river on his back, and the two monks went on their way back to the monastery.
A few days later, the young monk reproached the elder monk for his act which was unbecoming of a monk, and that he shouldn't have carried the woman on his back. The elder monk laughed, "I carried the woman across the river because she needed help, and I left her at the other bank of the river. Why are you still carrying her in your mind?"