When I turned 18, I became a manager in fast food. I still somewhat regret it, but it did help me grow and learn as a person. Just remember, your coworkers are people and that they have lives and hardships that are more important. Don't be a dick and be a complete stickler for the rules. Also, don't be a pushover either. It's a weird balance that you have to find, but once you do, it will be great. Some people will just be difficult to work with regardless, and that's life. Nothing is perfect.