Doctor Frog
Long ago, cheerful animals lived by the edge of a green forest where cool waters flowed. In this beautiful forest, there was a small and muddy pond. A green frog living in the pond suddenly declared himself a very knowledgeable doctor. Gathering all the animals, he boastfully said he could cure any disease. "I know all the medical science in the world, I find a cure for every trouble," he shouted.
A wise fox passing by looked at the frog's muddy and spotted skin. The fox smiled and asked the frog. "While you cannot heal your own muddy skin and illness, how will you heal others?" he said. Ashamed, the frog dived back into his muddy water.
He who cannot cure his own trouble cannot be a doctor to others. Liars are exposed sooner or later. First, one must correct one's own shortcomings. Unconvincing claims quickly crumble. He who is of no use to himself cannot help others.
Empty boasting humiliates a person. True knowledge does not require showiness. An architect who cannot build his own house cannot be an architect. Fake expertise is quickly exposed. Knowing oneself is the greatest wisdom.