What thoughts are you holding on to?

Two monks were walking along the bank of a swift river. There they met a young woman who could not cross alone. One of the monks picked up the young woman and carried her across the river to the other side.
     Sometime much later, the other monk said to his companion, “Did you forget that it is against the rules to touch a woman? Have you forgotten the vows you have taken?”
     The other monk answered, “Brother, I left the young woman on the bank of the river once we crossed. Why are you still carrying her in your mind?”