In The Fast Lane Meaning

(idiomatic) In a lifestyle, employment position, or other set of circumstances where the rapid pace is exciting, frantic, or risky.

Example: 2003, B. Krandrowitz and K. Springen, "Free At Last!," Newsweek, 13 Oct.:
  For baby-boomer parents, life without kids often feels like suddenly slamming on the brakes after years in the fast lane.
2005, Claudia Wallis, "AIDS: A Growing Threat," Time, 18 Apr.:
  He readily admits to a life of promiscuity and a history of many liaisons with prostitutes. "I lived in the fast lane," he confesses.