Bhagavad Gita, Chapter 6, Verse 34

Verily, the mind, O Krishna, is restless, turbulent, strong, and unyielding. I regard it quite as hard to achieve its control, as that of the wind.

Arjuna isn't wrong to find this hard, the mind really is described as genuinely difficult to hold still.

This names the real challenge in concrete, relatable terms. Comparing the mind to something as untamable as wind validates that this struggle isn't imagined or exaggerated, it's a real and serious difficulty.