from Wiktionary, Creative Commons Attribution/Share-Alike License
- Life is full of surprises, you never know what will happen next.
Often thought to have appeared in the 1994 film Forrest Gump, when the lead character Forrest Gump (played by Tom Hanks) says "Mama always said life was like a box of chocolates. You never know what you're gonna get." (Wiktionary)