When Clara Silverstein turned 40, she wanted to realize her dream of running a marathon. But she had never been much of a runner, and her first attempts were more difficult than she imagined. "I was so sore and winded, I almost gave up," says Silverstein. Instead, she adjusted her expectations and eased into running. "Forget about running a mile on your first outing," she says. "Walk first to warm up, then run for five minutes or less. Running is not going to feel natural at first because you need to give your body time to adjust." Over the weeks, she alternated walking and running during the same workout, until about two months later, when she could run 30 minutes without feeling winded. In 2008, seven years later, she accomplished her goal: Silverstein ran her first marathon in Richmond, Virginia. Today, the busy cookbook author and mom runs two to three times a week, but walks once or twice a week as well. "I never could have even considered running without being a regular walker first," she says.