The official motto for this month’s Summer Olympics in London is simple: “Inspire a generation.”If each of the athletes had their own personal slogan, Shalane Flanagan’s would be a little more direct and to the point: “Leave nothing to chance.”The pride of Marblehead leaves the United States today for Europe, where she and her fellow U.S. Track & Field teammates will settle in the Netherlands before eventually making their way to London. Flanagan will be running her first Olympic Marathon (and only her third marathon ever) on Sunday, Aug. 5, and has left absolutely no stone unturned as she prepares for the biggest race of her life.“When I step on that starting line, I want to have absolutely no regrets about my preparation,” said Flanagan, who celebrated her 31st birthday on July 8. “If anything is within my control and I can control it this time, I will. I’m taking full responsibility for everything that I do.” To illustrate her point, Flanagan will not be taking part in the Olympics’ Opening Ceremonies this Friday night. It’s not because she’s done it twice already (2004 in Athens and 2008 in Beijing) or that she wouldn’t liketo do it, but more because it’s the smartest choice to make in terms of her marathon preparation.“Most of my teammates will, but Kara (Goucher, a close friend of Flanagan’s and fellow U.S. marathoner and training partner) and I won’t. Being on our legs for six to seven hours that night doesn’t sound like a lot of fun,” the former Marblehead High and University of North Carolina superstar admitted