Knowing others is intelligence,
Knowing your self is true wisdom.
Mastering others is strength,
Mastering your self is true power.
If you realise that you have enough,
you are truly rich.
One who keeps his course
surely lives long.
One who gives himself to the Tao
surely lives forever.
This is a famous verse of the Tao, particularly the first two sentences. The whole essence of the Tao Te Ching seems to be pointing us away from undue focus on the outward forms – on other people, situations, and events (basically the very stuff that tends to perpetually occupy most people to the point of obsession) – and back to the inner self, which is rooted in the Tao, yet which is largely unnoticed by all but a few.
It often seems like we know everything there is to know about the world and universe around us, but absolutely nothing about who and what we truly are. Therefore, knowing ourselves is of prime importance and brings a wisdom that runs far deeper than the surface-level knowledge we have of the outer forms.
Mastering that self, rising above the unconscious content of the mind and ego to embody that which is most authentic and real within us, is power in its truest, most unshakable sense.