What is that joyfulness?

People think, "I can enjoy this material world very nicely. Everyone is having such a good time. There is no reason I can't enjoy myself as much as they." This idea is illusion because there is no real enjoyment in the material world. We may be very good-looking, famous, well educated, wealthy and powerful, and we may have a very beautiful wife and children and hold the highest position in the country—but at any moment we are subject to be shot down. This is the nature of this world. There is no question of having pleasure without impediments. Even when the pleasures are earned after a great deal of struggle and sacrifice, they are temporary. In this material world there is no pleasure that can give us constant and unending enjoyment. One has to understand he is not the material body. Then one immediately becomes joyful. Just like if you are implicated in some undesirable affair and your lawyer advises, "Oh, you are free from this implication. The law does not bind you," you feel pleasure, "Oh, I'm free from this implication?" "Yes," similarly, as soon as one is convinced that "I am not this material body," then immediately he becomes joyful. What is that joyfulness? There is no hankering, no lamentation. Only Krishna can give us that. Therefore Krishna instructs in Bhagavad-gita that it is the welfare of every living entity to give up this material activity and just surrender unto Him, He will give protection from all sinful reactions. Unfortunately, people are so attracted by the glitter of material nature that they cannot do it. People always fear that by surrendering to Krishna they will lose something but Krishna is so kind that if He takes anything away, He will reward us a thousand-fold.

Ref: Chapter 8c, Science of Self Realization authored by Srila Prabhupada (Founder - Acharya, ISKCON)