। ॥ ६३७ ॥
In plain words
Mistaking the gross and subtle bodies—which are inherently sorrowful—for their own self, and forgetting the blissful nature of the true Self, the ignorant person seeks happiness from sources that only deliver pain.
Close to the Sanskrit
The gross and subtle body, inherently of the nature of sorrow, having grasped as one's own self, and having forgotten the own bliss-form of the self, from the givers of sorrow happiness the ignorant one desires.