I don't have an all time favorite quote, just like I don't have an all time favorite meal - I have some years, as they say in other languages than english, and memories are too rich to parse that way.
But here's one I like, by Dante Alighieri in the Inferno section of the Divine Comedy -
Nel mezzo del cammin di nostra vita,
Mi ritrovai per una selva oscura,
Che la diritta via era smarrita.
When I had journeyed half of our life's way,
I found myself within a shadowed forest,
for I had lost the path that does not stray.
Admittedly I like it for the sound and meaning in italian more than in translation. (often written as 'in a dark wood')