Bhagavad Gita, Chapter 5, Verse 20

Resting in Brahman, with intellect steady, and without delusion, the knower of Brahman neither rejoices on receiving what is pleasant, nor grieves on receiving what is unpleasant.

Real steadiness looks less like never feeling anything, and more like not swinging wildly with every good or bad thing that happens.

This isn't describing numbness, it's describing genuine balance. Good news doesn't inflate someone that grounded, bad news doesn't collapse them either, both are met from the same steady place.