Hilarious, outgoing and always up for a good time, New Yorker Brittany Forgler (Jillian Bell)  is 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…