"Carpe diem," as you probably already well know, means "seize the day" or, less literally, "make the most out of the time we have." The phrase is often credited to the Roman poet Horace (or Quintus Horatius Flaccus). It's a pretty common sentiment in literature. For example, Henry David Thoreau talks in Walden about "want[ing] to live deep and suck all the marrow out of life."
Andrew Marvell's poem "To His Coy Mistress" opens famously with the assertion that, if we had all the time in the world, we would have no need to hurry with our passion:
Had we but world enough, and time,
This coyness, lady, were no crime.
The second section counters this first section by making clear that we, in fact, do not have al the time in the world:
But at my back I always hear
Time's winged chariot hurrying near;
The third and final section of the poem brings this argument to a close ("therefore") by urging the "coy mistress" to act with him now on their love:
Now therefore, while the youthful hue
Sits on thy skin like morning dew,
Most readers see this poem as presenting a thinly-veiled and self-serving argument. The speaker wants a woman to go along with what he wants, which is her now. The sentiment of "carpe diem," apparently, can be either thoughtful or superficial.