Moksa Opadesa Yoga: Bhagavad Gita Chapter 18 [Final Revelations of the Ultimate Truth]
Krishna Said > Shaloka: 36
English
O best of the Bharatas, now please hear from Me about the three kinds of happiness which the conditioned soul enjoys, and by which he sometimes comes to the end of all distress. That which in the beginning may be just like poison but at the end is just like nectar and which awakens one to self-realization is said to be happiness in the mode of goodness.
Purport
A conditioned soul tries to enjoy material happiness again and again. Thus he chews the chewed, but, sometimes, in the course of such enjoyment, he becomes relieved from material entanglement by association with a great soul. In other words, a conditioned soul is always engaged in some type of sense gratification, but when he understands by good association that it is only a repetition of the same thing, and he is awakened to his real Krishna consciousness, he is sometimes relieved from such repetitive so-called happiness.
In the pursuit of self-realization, one has to follow many rules and regulations to control the mind and the senses and to concentrate the mind on the self. All these procedures are very difficult, bitter like poison, but if one is successful in following the regulations and comes to the transcendental position, he begins to drink real nectar, and he enjoys life.