Time is too long for life,
For knowledge, not enough.
(The first line of a poem by Rosario Castellanos)
This line (the entire poem) has followed me my entire life. When I was a moody teenager, I took it the pessimistic way and figured, what was the point of anything?
Thankfully, I've grown up quite a bit since then, and now it's taken on a new meaning: life is short, live it fully, and you'll never stop learning - in fact, you can never learn too much.