If you're after a good night's sleep, the belief that exercise helps you rest well is more important than exercise itself, says a new Swiss study published in the U.S. "The most practical advice that science can offer at the moment about exercise and sleep is not to fret too much about whether you’re getting enough of either. Worrying, as the Swiss study showed, is what will keep you awake long into the night. 'I would give the following recommendation,' Mr. Gerber, the Swiss scientist, wrote. 'It does not matter how much exercise” you actually complete “as long as it make you feel good and feel fit.'"