Epictetus compares the mind to a bottle of water with a ray of light shining through it, representing our perception of external events. If the water is shaken, the light is refracted and disturbed. Likewise, when our mind, judgements, and perceptions are internally disturbed, external events look disturbing to us. We project our feelings on to external events. The sage sees everything in the same light because his mind is constant and he refuses to attach undue importance to anything outside his control.
If you want anything good, get it from yourself.
The attainment of self-awareness and self-control.