Don’t Put All your Eggs in One Basket

Meaning:
This is a piece of advice which means that one should not concentrate all efforts and resources in one area as one could lose everything.

Example:
Mr Tan’s financial adviser urged him to be careful and not put all his eggs in one basket by investing all his money on stocks.

Did you know?
This phrase was said to be first used in the novel “Don Quixote”, where it was written “It is the part of a wise man to keep himself today for tomorrow, and not venture all his eggs in one basket.”

Reference: http://www.goenglish.com/DontPutAllYourEggsInOneBasket.asp