"Foolishness is thinking a lot about what matters a little and a little about what matters a lot." (Piper on Heb 9.27 & Ps 90.12 as I noted it, though not quite as in script.)
"Moses put it like this in Psalm 90:12, "So teach us to number our days, that we may get a heart of wisdom."
Surely the writer of Hebrews wants us to hear this word of the Lord in [ch.9] verse 27 and be wakened from the usual numbness and sleepiness of our lives. Most people think very little about what matters most and think very much about what matters little. The Bible is God's gift to us to keep us from that foolishness and to make us wise. Wise people are people who have proportion in their lives. What matters most they are most concerned with, and what matters least they are least concerned with."