When I was 5 years old, my mom always told me that happiness was the key of life. When I went to school, they asked me what I wanted to be when I grew up. I wrote down "happy". They told me I didn't understand the assignment and I told them they didn't understand life.
Remarks about the translation
A friend of mine once showed this quote by (as far as I know) John Lennon, and I translated it into Dutch for her and she subsequently translated it into her language. As I sent the sentence to people from other countries, they also translated it and the resulting translations have fascinated me. I'd love to see the quote in the selected/requested languages. :-)