Advaita Vedanta Basics - Anandamaya Kosha

207. The blissful sheath (Anandamaya Kosha) is that modification of Nescience which manifests itself catching a reflection of the Atman which is Bliss Absolute; whose attributes are pleasure and the rest; and which appears in view when some object agreeable to oneself presents itself. It makes itself spontaneously felt by the fortunate during the fruition of their virtuous deeds; from which every corporeal being derives great joy without the least effort.

208. The blissful sheath has its fullest play during profound sleep, while in the dreaming and wakeful states it has only a partial manifestation, occasioned by the sight of agreeable objects and so forth.

209. Nor is the blissful sheath the Supreme Self, because it is endowed with the changeful attributes, is a modification of the Prakriti, is the effect of past good deeds, and imbedded in the other sheaths which are modifications.

Source: Vivek Choodamani