Psalm 90:12 (NIV) Teach us to number our days aright, that we may gain a heart of wisdom.
James 4:13-16 (TEV) 13 Now listen to me, you that say, "Today or tomorrow we will travel to a certain city, where we will stay a year and go into business and make a lot of money." 14 You don't even know what your life tomorrow will be! You are like a puff of smoke, which appears for a moment and then disappears. 15 What you should say is this: "If the Lord is willing, we will live and do this or that." 16 But now you are proud, and you boast; all such boasting is wrong.
Ephesians 5:15-18 (TLB) 15 So be careful how you act; these are difficult days. Don’t be fools; be wise: 16 make the most of every opportunity you have for doing good. 17 Don’t act thoughtlessly, but try to find out and do whatever the Lord wants you to. 18 Don’t drink too much wine, for many evils lie along that path; be filled instead with the Holy Spirit and controlled by him.
"We are always complaining that our days are few and acting as though there would be no end of them."—Seneca
Leadership, Vol. 5, no. 1. Elesha Hodge, comp., Today's Best Illustrations – Volumes 1-4, (Carol Stream, IL: Christianity Today, 1997), WORDsearch CROSS e-book, Under: "PHYSICAL LIFE".