“What are the best things and the worst things in your life, and when are you going to get around to whispering or shouting them?”

101 Ways to Make Every Second Count: Time Management Tips and Techniques for More Success With Less Stress (1999)

Source: Quoted in "The Overview Effect: Space Exploration and Human Evolution" by Frank White

Source: Abarat

Source: Whatever You Think, Think the Opposite

Source: At Swim-Two-Birds

Source: Vampires, Scones, and Edmund Herondale

As quoted by John M. Kost http://www.mackinac.org/bio.aspx?ID=104 (25 July 1995) in S. 946, the Information Technology Management Reform Act of 1995: hearing before the Subcommittee on Oversight of Government Management and the District of Columbia of the Committee on Governmental Affairs (1996).
This appears to derive from a 1910 advertisement by writer Alfred Henry Lewis for a forthcoming series of biographical articles about Roosevelt: "All activity, Mr. Roosevelt has often shown that it is better to do the wrong thing than do nothing at all. In politics this last is peculiarly true. The best thing is to do the right thing; the next best is to do the wrong thing; the worst thing of all things is to stand perfectly still". (e.g. in La Follette's Magazine https://books.google.com/books?id=RV4CAAAAIAAJ&pg=PA183&dq=%22best+thing%22+%22right+thing%22+%22worst+thing%22+nothing&hl=en&sa=X&ved=0ahUKEwjNksu-nZrMAhVDy2MKHSl1Df8Q6AEIIzAB#v=onepage&q=%22the%20best%20thing%20is%20to%20do%20the%20right%20thing%22&f=false (28 May 1910)
Disputed

Happy Farmers
Alain On Happiness (1928)

Source: The Count of Monte Cristo