Carpe diem is a Latin aphorism, usually translated "seize the day", taken from book 1 of the Roman poet Horace's work Odes (23 BC).
Carpe is the second-person singular present active imperative of "pick or pluck" used by Horace to mean "enjoy, seize, use, make use of".Diem is the accusative case of the noun "day". A more literal translation of "carpe diem" would thus be "pluck the day [as it is ripe]"—that is, enjoy the moment.
Text from Odes :
Tu ne quaesieris, scire nefas, quem mihi, quem tibi
finem di dederint, Leuconoe, nec Babylonios
temptaris numeros. ut melius, quidquid erit, pati.
seu pluris hiemes seu tribuit Iuppiter ultimam,
quae nunc oppositis debilitat pumicibus mare
Tyrrhenum. Sapias, vina liques et spatio brevi
spem longam reseces. dum loquimur, fugerit invida
aetas: carpe diem, quam minimum credula postero.
Ask not ('tis forbidden knowledge), what our destined term of years,
Mine and yours; nor scan the tables of your Babylonish seers.
Better far to bear the future, my Leuconoe, like the past,
Whether Jove has many winters yet to give, or this our last;
This, that makes the Tyrrhene billows spend their strength against the shore.
Strain your wine and prove your wisdom; life is short; should hope be more?
In the moment of our talking, envious time has ebb'd away.
Seize the present; trust tomorrow e'en as little as you may.
Perhaps the first written expression of the concept is the advice given by Siduri to Gilgamesh, telling him to forgo his mourning and embrace life although some scholars see it as simply urging Gilgamesh to abandon his mourning, "reversing the liminal rituals of mourning and returning to the normal and normative behaviors of Mesopotamian society."
In Horace, the phrase is part of the longer carpe diem, quam minimum credula postero, which can be translated as "Seize the day, put very little trust in tomorrow (the future)". The ode says that the future is unforeseen and that one should not leave to chance future happenings, but rather one should do all one can today to make one's future better. This phrase is usually understood against Horace's Epicurean background. The meaning of "carpe diem" as used by Horace is not to ignore the future, but rather not to trust that everything is going to fall into place for you and taking action for the future today.