There are two phrases here: carpe diem, meaning "seize the day"; and vita brevis, meaning "short life."
"To His Coy Mistress" by Andrew Marvell, "To the Virgins, to Make Much of Time" by Robert Herrick, "Song" by Sir John Suckling, and "Carpe Diem" by Horace all have a theme based on carpe diem.
it Doesn't change
To have fun at that moment in time, with no worries of the future
This is the popular saying which means Seize the day without fear