दुःखप्रत्ययशून्यत्वादानन्दमयता मता ।अज्ञाने सकलं सुप्तौ बुद्ध्यादि प्रविलीयते ॥ ५६२ ॥
In plain words
Its blissfulness is simply the absence of any experience of sorrow. During deep sleep, the intellect and all mental faculties completely dissolve into ignorance.
Close to the Sanskrit
Blissfulness is considered [to be so] due to the absence of painful cognitions; in deep sleep, all [things] like the intellect dissolve entirely into ignorance.