(1) "You can’t take it with you." (Referring to money and death, but I believe this extends to everything.)

(2) "Life moves pretty fast. If you don’t stop and look around every once in a while, you could miss it." (From Ferris Bueller’s Day Off, though it might not be verbatim.)

3) "Today is the first day of the rest of your life." (I don’t know the source of this.)

Quoting myself here, though I realize this isn’t as elegantly worded as it could be:

(4) "Whenever you find yourself faced with a choice between doing something and not doing something, and you’re undecided, always make the choice that involves doing something."