You must read Śrī Caitanya-caritāmṛta, from beginning to end;
and after this, Śrīmad-Bhāgavatam from top to bottom.
We are engaged in devotional services throughout the day, but
within this time we must somehow take some time – in the night or
the day – to study. In a single day, Śrīla Rūpa Gosvāmī and Śrīla
Sanātana Gosvāmī sometimes slept approximately three hours, and
sometimes they did not sleep at all. Śri Caitanya Mahāprabhu
did not sleep at all in the day or night. It is essential that we also curtail
our sleeping. In my young age, and then after I took sannyāsa up
until the old age of seventy-five, I never slept in the daytime. In the
daytime I used to go to the garden of our maṭha, or to a park, even
in the heat, and I would read all the scriptures. I request that you also
do this. A gṛhastha works very hard, performing many activities
throughout the day, and it is to our advantage to do ten times more than
that in kṛṣṇa-bhajana. Kṛṣṇa-bhajana is our life and soul. After this life is
finished, we do not know what birth we will take.

―Śrīla Bhaktivedanta Nārāyaṇa Mahārāja