In this world, man is a target of death, an easy prey to calamities, here every morsel and every draught is liable to choke one, here one never receives a favour until he loses another instead, here every additional day in one's life is a day reduced from the total span of his existence, when death is the natural outcome of life, how can we expect immortality.
Allah, the Exalted, gave the angels intellect without desires, He gave the animals desires without intellect, and He gave both to the sons of Adam. So a man whose intellect prevails over his desires is better than the angels, whilst a man whose desire prevails over his intellect is worse than the animals.
How strange and foolish is man. He looses his health in gaining wealth. Then to regain health he wastes his wealth. He ruins is present while worrying about his future - but weeps in the future by recalling his past. He lives as though death shall never come to him - but dies in a way as if he were never born.