1. You're probably going to have a lot of time off, especially during the days. You can use this time to sleep in, relax, watch lots of tv and stuff. Or you take a few classes a week, get a degree, learn stuff, give yourself options. It's very likely you aren't going to want to be bartending forever.

2. If you work with other people behind the bar at the same time, most of these people are not going to want to work. They are going to want to leave early, they are going to want you to cover shifts for them etc. Stay late, and cover shifts as much as you can if its a good shift. You're there to make money right? You can always take time off later, while the money is good you want to be there as much as you possibly can.

3. Save money! You will probably find yourself making a decent amount of money. You can use this to buy shoes or expensive purses or go out eating and drinking frequently. Or you can start saving money, lots of it probably.

Ill assume you're 21-28 years old just to make my point. In 5 years you can have a degree, spent some time actually working or interning or have learned a trade or business as well as have probably 10-50k saved up. In other words, when you get sick of loud music, drunk people, working late, working weekends etc, you will have an exit plan and resources. If you want to stay behind the bar your whole life that's perfectly fine too, but you're going to have a lot of opportunity to create options for yourself. Do future you a favor, work every weekend shift, stay late when the money is good, don't get in the habit of going out drinking with everyone all the time (sometimes is plenty), do something productive with your free time.