Hilarious, outgoing and always up for a good time, New Yorker Brittany Forgleris everybody's best friend -- except maybe her own. At 27, her hard-partying ways, chronic underemployment and toxic relationships are catching up with her, but when she stops by a new doctor's office to try to score some Adderall, she gets slapped with a prescription she never wanted: Get healthy. Too broke for a gym and too proud to ask for help, Brit is at a loss, until her seemingly together neighbor Catherine pushes her to lace up her Converse sneakers and run one sweaty block. The next day, she runs two. And soon, after finishing her first mile, she sets an almost unthinkable goal: running in the New York City Marathon.