"I don't know."
Clench one fist for "I know", then clench the other for "I don't know". They're two versions of the same emotion: fear. One is borne out of fear of being wrong, the other fear of not being enough.
"I know" and "I don't know" both make the mind clench up.
They're complete opposite thoughts that yield the same detrimental result: your growth stops.
They're complete opposite thoughts with the same prescription: open your fists, let go, and choose curiosity over fear.