When I was 5 years old, my mother always told me that happiness was the key to 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.   -- John Lennon

Working Class Hero, by John Lennon:

https://www.youtube.com/watch?v=4lKwXwU5iWs