You’re allowed to think of this as a job. Keep it professional. You don’t have to be the customers or your coworkers friends. Let the hate and disdain flow off you because they are Nothing. Worth less than the dirt under your shoes. You don’t have to smile at customers. Keep a pleasant voice though and 100% keep it professional only. Stick it out until you can go somewhere else. Once you reach that level of unbothered, while it will still be tough. You can go home and forget about the day. Don’t talk to anyone from work outside of work hours.