Sri Muruganar:

Since the actual truth of their own experience is expressed by everyone thus, “I woke up from sleep; I slept happily,” it is agreed by everyone that Self shines as the form of happiness in the natural state of sleep, where the mind is empty and devoid of attachment to sense objects.

If it is asked why that happiness, which existed as one’s own nature in that state, ceases to be experienced as soon as sleep comes to an end, it is because of one’s desire to run after sense-objects, having been separated from one’s own state.

Therefore it is advised that one should attain the unsurpassed happiness which is one’s own true experience, by keeping the mind unshaken by the desire for sense-objects, which arises due to delusion, by knowing oneself and by shining without inattention [pramada], remaining peaceful even in the waking state as in sleep.