Whereas Prakṛti is continually active, Puruṣa is static (passive and not changing).
As Puruṣa cannot be the agent of any activity, it is merely an onlooker or enjoyer of the world. Anything that happens to Puruṣa is because of the activity of Prakṛti.
Prakṛti and Puruṣa always work together, though, like body and spirit. Together, they produce our experience of the world.