The difference between knowing the path and walking the path

When he was a young boy, Tzaji and his teacher were traveling together. At one point, they came to a river with a strong current. As they were preparing to cross the river, they saw a very young and beautiful woman also attempting to cross. The young woman asked if they could help her. His teacher carried the woman on his shoulder, forded the river and let her down on the other bank. Tzaji became quite confused and very upset, but said nothing. After walking for some time the teacher noticed that Tzaji was suddenly silent and inquired "Is something the matter? You seem very upset." To this Tzaji replied, "As monks, we are not permitted to be with a woman, so how could you then carry that woman on your shoulders?" The teacher replied, "I left the woman a long time ago at the bank, however, you seem to be carrying her still." At this, Tzaji fell silent in deep thought, and eventually in understanding. He and his teacher continued their journey.