In plain words
Every creature in the world wants happiness, not sorrow. Some hope for happiness from money, some from gold, some from goods, some from vehicles; in this way each looks for happiness from one thing or another. But those who know, or have come to know, what real happiness is are very rare. Happiness is of three kinds. It is like poison at the beginning and like nectar in its ripening. This is the happiness won by a Buddhi set on the Ātma, sāttvic happiness. That is, while practising the disciplines of śama, dama and the rest, one has to labour very hard. So at the beginning it is like poison, very painful. In the Yoga Vāsiṣṭha, “O Rāma! Even the great ocean can easily be drunk. Even the Sumeru mountains can be pulled up with ease, and fire can be eaten without effort. But mastery of the Manas is very hard,” said Vasiṣṭha. So once we have achieved that mastery of the Manas, that itself is immortality. Before attaining such immortality, the chief task is to strive for mastery of the Manas without calling it too hard. This is the first happiness.