A blind man cannot give instructions regarding anything concerning the visual properties of objects, so the teachings of a person who has not himself realized truth, cannot relate to any realizable principle.
Men with minds dominated by the principle of Tamas, lack the ability of discrimination between right and wrong and engage in vicious act or acts which cause great unhappiness. They are deluded and have wrong knowledge about the nature of ultimate reality.
What is a clod of earth today becomes a pot tomorrow. In the pot the earth is not destroyed; only the earth has changed form and is existing in the form of a pot.
Happiness or sorrow cannot be controlled by itself; it is to be eliminated by shutting out valid cognition etc. which give rise to them.
Source - Yoga Philosophy of Patanjali by Swami Hariharananda