BALLSTON SPA — Russell Shapiro has been working in the deli business since he first opened a shop in 1991 in Westchester County. Shapiro, who is set to turn 59 this year, now wants to take a step back from the industry, deciding to sell Russell's Deli on Milton Avenue in Ballston Spa. “This is a very difficult business,” he said. “You work seven days a week and a lot of hours, and I don’t physically, financially or for any other reason need to do it that much anymore. I love the business — it's been a passion of mine all…