Albert Einstein - If A is success in life, then A = x + y + z. Work...

Quote Text: 

If A is success in life, then A = x + y + z. Work is x, play is y and z is keeping your mouth shut.

Explanation: 

This was apparently said to Samuel J Woolf, Berlin, Summer 1929. It was also cited with additional notes in The Ultimate Quotable Einstein by Alice Calaprice and Freeman Dyson, Princeton UP (2010) p 230