During my time as a seasonal employee, I had plenty of work-life balance. I was able to comfortable an online class, work, and still see family and friends. It's up to you to communicate clearly when/how much you are able to work. I had great managers who posted the schedule about two weeks in advance, so there were never surprises on when I was expected to be at work, and I just worked around that schedule.
One can have a work life balance. It is important to take care of oneself especially during the holiday season which is busy. Coordinate self-care before work as one's work schedule can fluctuate. Eats lots of fruits and veggies and drink water because you will be talking a lot with customers.