One of my favorite ones is from Forrest Gump, "My momma always told me life was like a box of chocolates, you never know what you're gonna get."
Maybe the quote I'm going to write doesn't count, as it is not from a movie but a TV series, but it's my all-time favorite quote:
"Let me give you some advice, b*s***d. Never forget what you are, the rest of the world will not. Wear it like armour and it can never be used to hurt you." - Tyrion Lannister - Game of Thrones
"Fat, drunk, and stupid is no way to go through life, son".
-Dean Wormer, Animal House