When you walk into a store/restaurant/coffee shop/a place of business, please leave your attitude at the door. Treat the employees as if you are a guest in their space. Employees are not targets for your personal problems, and they do not turn off with the lights at night. Do not belittle them based on their place in the company, as everyone starts off somewhere. Do not get angry at cashiers for offering store programs as it is their job (imagine how frustrating it must be to be yelled at just for doing your job, repeatedly, throughout the day, for hours)- just politely decline. Just get in, get what you need, be courteous, and leave. Simple as that. Have a wonderful day.