The goal of mastering is to bring out the best of your mix. Without it, you’re simply selling your mix short by not allowing it to reach its full potential. Additionally, you run the risk of having translation issues when your song or album is played on many different sound systems, of widely varying quality. A mastering engineer’s goal is to ensure your mix translates well in the car, the club, the hi-fi audiophile setup, and even the tiny PA system at your local supermarket. Your mix deserves to sound great everywhere, and not just the room it was mixed in and the speakers it was mixed on. If you take your music seriously, professional mastering is absolutely VITAL.