Was watching Dead Poets Society the other day actually. I therefore suggest you also read Robert Herrick's poem 'To the Virgins, to Make Much of Time' in full, but I have been kind enough to put it here:

Gather ye rosebuds while ye may,
Old Time is still a-flying:
And this same flower that smiles to-day
To-morrow will be dying.

The glorious lamp of heaven, the sun,
The higher he's a-getting,
The sooner will his race be run,
And nearer he's to setting.

That age is best which is the first,
When youth and blood are warmer;
But being spent, the worse, and worst
Times still succeed the former.

Then be not coy, but use your time,
And while ye may, go marry:
For having lost but once your prime,
You may for ever tarry.