A lesson you have learned in life?

[KillerGremlin]

Age 17

Lesson Learned: Don't use shampoo.

...and, on a more *serious* note, I have a whole motto. It's not original or anything, and you hear people say it every once in a while, but meh, what the hell:

The only guarantee in life is death. Live each day like you are embracing your last.

Also, it's not worth worrying about tomorrow. Tomorrow will come, regardless. So why the hell get worried about it? Embrace tomorrow in the best way possible.