Nartaka ātmā नर्तक आत्मा॥ (sūtra III.9)

Nartakaḥ - dancer; ātmā – self.

Such an aspirant, who has entered the stage of unmanā, carries out his actions, as if a dancer performing yet another show. Dancing in this aphorism refers to action. Such a realised soul performs his routine as if he is acting. An actor is not the character that he depicts. In the same way, an advanced spiritual practitioner discharges his prescribed duties as if he is acting on a stage. He expresses happiness or sadness, he undergoes pleasures and pains, but he does not get attached to these emotions. His expressions and emotions are like an actor exhibiting his skills. An actor assumes many roles and he cannot become the characters that he assumes only on the stage. Thus, he conceals his real nature from the audience. Similarly, a practitioner who has attained unmanā stage carries out his routine actions devoid of emotional involvement. He knows that except Self, everything else is delusory.

This can be explained in yet another way. Śiva is the actor. His real nature is concealed by Śaktī through Her spell of māyā. Śiva exhibits His actions through Śaktī, thereby concealing His True Self. Śiva’s True Self is to perpetually remain in the purest form of consciousness, from which everything evolves and into which everything dissolves. In exhibiting His Self in the form of universe, he assumes the role of an actor. 

This aphorism says that a spiritually advanced person also postulates himself in normal human activities. He does not proclaim himself as a realised soul as he has already dissolved his ego. There is no necessity for him to proclaim himself to the world, as he feels more comfortable in His Company. He remains in perpetual bliss.