"A Psalm of Life" by Henry Wadsworth Longfellow was first published in 1838 in The Knickerbocker, when Longfellow was thirty-one years old. As would have been typical of his period, he was raised in a Christian environment and the poem is overtly framed as a response to the Book of Psalms of the Old Testament. Many of the psalms are lamentations, emphasizing that life on earth can be one of misery or exile, and that one must respond by trusting in God. The most exact Biblical quote actually occurs in Longfellow's lines:
Dust thou art, to dust returnest,
Was not spoken of the soul.
This echoes what God said when exiling Adam and Eve from the garden of Eden in Genesis 3:19 (not actually part of the Psalms):
In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return.
The phrase "dust thou art, and unto dust shalt thou return" is also used in the ceremony of the imposition of Ashes on Ash Wednesday.
What Longfellow is suggesting in the poem is that while humans are mortal and may experience many misfortunes, the appropriate response is not passive acceptance of external circumstances but instead an active endeavor to control one's own destiny. One should be heroic in striving to attain one's ideals and aspirations. People should emulate "great men" and leave behind them "footprints in the sands of time" which can inspire others rather than reacting passively like cattle to external circumstances. Even though people's bodies are mortal and shall "return to dust," their actions and works can be immortal. In conclusion, he recommends an active life of striving to achieve great goals.