The heading for Psalm 90 indicates Moses is the author.
One writer suggests “that the Psalm be heard as though Moses were now at Pisgah (Deuteronomy 34). He has come to the end. He stands looking at the promised land to which he has been ehaded all his life. Now it dawns on him that he will not go there. He embraces that painful reality that his life-pursuit of fidelity will short of fruition. He submits to that reality from God – but that does not stop the yearning” (Walter Brueggeman, The Message of the Psalms).
Moses says “life is hard.,” and as if it were not hard enough, there is the added difficulty of God’s expectations
Moses prays for help from God, but he also asks God to help us get the right perspective. Since our days are “numbered,” he prays for wisdom on God’s people that they might use their time wisely. He also asks that God make them successful in acting wisely. When you examine it in this light, it’s a prayer we could all pray.