Most of my favourite quotes are actually song lyrics... one that really stood out to me, was from a band called Sum 41, in a song called Fat Lip:

"I don't want to waste my time, becoming another casualty of society"

Another quote which had an incredibly profound effect on me, actually came from my best friend's mother, who said:

"I always wonder if people realise that they don't get to see their own funerals..."

I don't really agree with it, but I like it:

"Why should the generations overlap one another at all?  Why cannot we be buried as eggs in neat little cells with ten or twenty thousand pounds each wrapped round us in Bank of England notes, and wake up, as the sphex wasp does, to find that its papa and mamma have not only left ample provision at its elbow, but have been eaten by sparrows some weeks before it began to live consciously on its own account?"

--Samuel Butler, The Way of All Flesh

And my favourite one :)

Qué es la vida? Un frenesí.
¿Qué es la vida? Una ilusión,
una sombra, una ficción,
y el mayor bien es pequeño:
que toda la vida es sueño,
y los sueños, sueños son.

~ Pedro Calderón de la Barca