Sometimes life seems to be crawling along and at other times speeding by at warp speed. Moses wrote the 90th Psalm and I bet he knew something about waiting. He waited 40 years for God to rescue the Jews from their Egyptian oppressors until he took matters into his own hands and killed an Egyptian who was beating a fellow Hebrew.
When he fled into the desert of Midian he watched sheep for 40 years until he heard God's voice in the burning bush. I can't imagine anything that might make a day seem longer than watching sheep eat grass. He waited for Pharaoh to soften his heart and it took 10 terrible plagues before he relented. Then he endured another 40 years of whining wanderers only to miss out on his chance to enter the Promised Land.
With this kind of experience, Moses wrote in verse 12 "Teach us to number our days that we may gain a heart of wisdom." My favorite definition of wisdom is knowing what is most important and acting accordingly. It is the second part of the definition that is so difficult because I think most of the time we truly know what is most important, however we don't choose to act accordingly. If we really realized how precious our time is here on earth we would treasure each day and leverage it, using it for maximum eternal impact, not wasting our time on activities that have no everlasting value. Go and seize the day for the Lord!