What does Psalm 103:15 mean?

David continues to comment on the brevity of human life. He compares its fragility to grass and flowers. The climate is dry in the areas around Jerusalem, so smaller plants have brief, delicate lives. They flourish only in the rainy season. They can shrivel away and be gone relatively quickly.

Humans, too, flourish for only a brief time. Even well-conditioned athletes consider their prime years ended before the age of 40. If they are going to excel in their sport, they need to do so when they are young. Advancing age causes a human being's stamina and general health to fade. In the workplace an employee's best contribution to productivity is often considered to come between the 20s and 50s. By the time an employee reaches 65, the company he works for may pressure him to retire. Even by age 40 hairlines may recede and by mid-50s wrinkles may appear on one's face. No wonder the writer of Proverbs 27:1 cautions: "Do not boast about tomorrow, for you do not know what a day may bring."