My two favorite Psalms that help me remember how short my time is here on earth are Psalm 39 and Psalm 90. Psalm 90:12 is my constant prayer and scripture I scribble in my planner every year: "Teach us to number our days, that we may gain a heart of wisdom."
"Show me, Lord, my life's end
and the number of my days;
let me know how fleeting my life is.
You have made my days a mere handbreadth;
the span of my years is as nothing before you.
Everyone is but a breath,
even those who seem secure.
"Surely everyone goes around like a mere phantom;
in vain they rush about, heaping up wealth
without knowing whose it will finally be.
"But now, Lord, what do I look for?
My hope is in you." -- Psalm 39:4-7 (NIV)
I really want to make my days count. I don't want to take anything for granted. And because it is so easy to get carried away by a million things going on around me, I have to make a deliberate effort to put God first each day. Every year I make an effort to read through the Bible. In between there were two - three years where I studied the New Testament in depth (Jesus' teachings in the gospels, Paul's letters, humility), and then just the Old Testament! There is so much to drink deeply of in the word. "To all perfection I see a limit; but your commands are boundless." -- Psalm 119:96 (NIV)