Devotional Service is bliss!

Verse 1.5.3 to 5: Vyasadev was sitting on the banks of Saraswati, after having written all the Vedic literature. He was not happy though. So here, Srila Prabhupada writes that a person who knows all the knowledge, why is he unhappy? For example, if a person achieves the success of such a huge task of compilation of Vedic literature, then how come he is miserable.
It is explained again and again, Pure Devotional Service is very very pleasing to the heart.
A person who executes devotional service, gets a drop of Krishna's mercy, then he is submerged in the ocean of transcendental bliss.
Eg: Shyamananda Pr, Srinivas Acharya and ... were students under Jiva Goswami. When Shyamananda Pr touched the anklets of Srimati Radharani, we was totally submerged in spiritual bliss, then he knew this ankle bell was not of some ordinary woman. Lalita-sakhi's transcendental form was seen in due course by Shyamananda Pr. It was so beautiful transcendental form.

In that way, devotional service brings complete bliss.
Likewise, chanting initially it bitter. But when we keep on chanting, we completely purify ourselves, and we see Krishna and Krishna's lila when chanting, and hence we enthusiastically chant the Hare Krishna Maha mantra.

So here, Vyasadev wrote only about the business dealings of the material world, so he was not happy internally. Only after writing about Krishna and His pastimes, did he get that satisfaction that he was missing.