Bhagavad Gita, Chapter 2, Verse 65

In that peace, all sorrow is destroyed. For the mind of one who is peaceful soon becomes steady.

Real peace doesn't just feel good in the moment. It settles something permanently.

The kind of peace described here isn't a temporary mood, it's described as sorrow actually ending, not just being managed. Once that settles in, the mind stops drifting and finally has somewhere solid to rest.