Be thankful for what you have; you'll end up having more. Oprah Winfrey

Be thankful for what you have; you'll end up having more. If you concentrate on what you don't have, you will never, ever have enough. - Oprah Winfrey 

 Develop an attitude of gratitude, and give thanks for everything that happens to you, knowing that every step forward is a step toward achieving something bigger and better than your current situation. - Brian Tracy 

Further reading: Zero-Based Gratitude 

  Comparisons are odious