Bhagavad Gita, Chapter 7, Verse 30

Those who know Me with the Adhibhuta, the Adhidaiva, and the Adhiyajna, continue to know Me even at the time of death, steadfast in mind.

Real, deep understanding built over time is described here as holding steady even at the hardest possible moment.

This closes the chapter with a real, concrete test. Not whether someone can stay focused during ordinary circumstances, but whether that same clarity actually holds all the way through to death itself, described here as genuinely possible for those who've built it deeply enough.