Life, according to Job, is short and filled with troubles. Once death arrives, there is no chance of continuing life for a man. God determines how long a man should live. He is pleading with God to turn away his anger so that he does not endure these sufferings and complete his life in peace.
In certain ways, a tree is better than man. Even if a tree is cut down, it can sprout again and therefore has a second chance at life. Job longed for the grave and hoped for something better. He said that God has the power to hide him in the grave after his death and bring back to life after some time, if God was willing for a reconciliation.
Job now despairs by comparing the ultimate power of God. He felt completely defeated by God and mourned for all the disaster he was undergoing.