Emily Sisson, the fastest American female marathoner who set the record at the 2022 Chicago Marathon with a time of 2:18:29, has built her Boston training block around the mantra “For the fun of it.” While participating on a panel at the Boston Marathon Expo, she spoke about how she’s been learning to reframe the “all or nothing” mentality with the help of her husband Shane, who is a mental health therapist. “Two and a half hours is a long time to spend in your head, so make it a nice place to be,” Sisson said. She also shared her strategy for the marathon: She likes to think of the race in segments. For Sisson, the segments are bottle stations, small wins along the road to the finish line. The strategy, often called “chunking,” is great not only for marathons but also for long runs. Chunking can help you wrap your head around interminable distances and split it into much more manageable fragments. As you’d expect, RW staffers have learned lots of ways to trick themselves.…