While American long-distance stars Galen Rupp and Shalane Flanagan may headline the 30,000 runners who will participate in Monday’s 122nd Boston Marathon, it’s the rest of the field that gives the historic race much of its flavor. Runners from across the country and around the world who have achieved the event’s rigorous qualifying times converge on Hopkinton, Massachusetts, early in the morning to begin what for many is the pursuit of a bucket-list achievement. Through the ensuing hours that blend the pleasure of running along the fan-lined route to Boston and the pain of the physical challenge that marathon distance of 26.2 miles inevitably presents, individual runners with myriad personal goals evolve into a community of like-minded souls that embraces the Boston Marathon’s tradition anew. Katie Norwood, a 29-year-old from Bangor who works as a personal trainer at Wilcox Wellness and Fitness, experienced those feelings for the first time a year ago. “Honestly, I think doing the race last year made me fall in love with running just because of that Boston atmosphere,” said Norwood, one of 189 Mainers registered for this year’s race.