Moses wrote this Psalm during wandering in the wilderness following God’s sentence of 40 years life span upon the unbelieving Israelites who were 20 years of age and above. This psalm can be divided into three parts viz perspective, problem and prayer (3 Ps)
Getting the right Perspective (v 1-6).
God is sovereign (verses 1 and 2) – He is tremendous, tender and timeless (3 Ts). Keep this perspective in mind. But he is not so great and vast that he is remote and cold. He invites us to come and find our den in him. Moses moved on to develop this thought. Sympathy of God (v 3 and 4). God’s great eternal loving heart goes out to man in sympathy. God knows the tyranny the tomb and the time has over mankind. Moses brought out the severity of God’s judgment into sharp focus.
The real problem (v 7-12)
Moses now is speaking now of things taken right out of recent history, things with which the people who first sang this song were all too sadly familiar. In this section, he harps on 2 notes – man’s sin and God’s sentence. Our lives are sinful (v 7, 8). There is no such thing as secret sin in front of God. Our lives are so short (v 9, 10). An Israelite who was 20 died by the time he was 60. If he was 30, he died by the time he was 70 and so on. Their story was told. They could think about redemption from Egypt but they could never look forward to life in the promised land, Canaan. Our lives are serious (v 11, 12). The children of Israel knew the maximum years of life they will live following God’s judgment at Kadesh -Barnea. With us it is not known. No wonder the Spirit of God urges us to number our days and apply our hearts unto wisdom.
The resulting prayer (v 13 – 17)
Life which has its perspectives right, which has its greatest problems solved, will be occupied in a definite direction, which is clearly seen in Moses’ prayer. We see fresh evidence of the moving of God (v 13). He pleaded for God to return and for Him to repent of the righteous wrath and judgment He was preparing to send. Fresh enduement of the mercy of God (v 14, 15). The sands of time may be sinking but we can experience His lovingkindness, mercy and grace. Fresh experience of the might of God (v 16). It will be the young generation 19 years of age and below who will carry forward God’s purpose. Pray that God will use our children as well to continue His work. Fresh effulgence of the glory of God (v 17). Let us borrow that prayer. 
Conclusion – The psalm begins with the fact of God and then describes man’s plight coming back once again to God and His grace. Will you be consumed by His anger or saved by His grace? 
Dr. (Mrs.) Vanessa Kharmawphlang