After years in sales, Dan Di Cio, a Pittsburgh account executive, was aiming for “a breakout season” selling high-tech equipment. But even working longer hours and weekends, he kept falling short of his goals. Watching other salespeople win awards, he asked himself early this year: “Why can’t I be that guy?” To boost his self confidence during the recession, real-estate broker Tim Stowell, copied some tactics used by golfer Jack Nicklaus to improve the mental side of his game.Mr. Di Cio, a big baseball fan, recalled how Major League pitcher John Smoltz got help on his mental game to pull out of a slump in 1991. Mr. Di Cio contacted sports psychologist Gregg Steinberg after hearing him speak and, with his help, Mr. Di Cio learned that he was working so hard that he risked driving his numbers even lower. Dr. Steinberg says he prescribed the same remedy many pro athletes embrace: Stop overworking and allow yourself to relax.