Want a Happy Retirement?  Don't Just Guess About What You'll Need 
Chuck Saletta (DailyFinance, May 13, 2013)

"In its research, EBRI found that people who either used online retirement calculators or who worked with financial advisers were far more prepared to have a successful retirement than those who didn't. On the flip side, those who relied primarily on guessing at how much they'd need to cover their expenses wound up far worse prepared for their retirement than the typical person."

Not sure that the EBRI research actually measured happiness, but the conclusions in this article are 100% consistent with the themes expressed in this website--In these days when individuals are much more responsible for their own retirement, you need to do the retirement math--you need to crunch your numbers based on your financial situation.  And how much you can spend in retirement is just the other side of the retirement planning coin of how much you need to save to replace your pre-retirement standard of living.