Your day cannot and will not always go great if you expect everyone to be nice to you. If you intend to do business, and to stay in business, you will have to learn people management. Expect customers to be rude yet still buy from you. Expect some to be rude and never walk into your shop. The demeanour of a customer at any time during your working hours should not change your composure. Your duty is to be nice to all, at. At the end of the day make your sale, and carry on with normal business activities. Whenever a customer is rude, yet you return the favour by being nice, it won't be the last time you see such a customer. Most of the time, you both end up becoming friends. If you know the attitude of your customers, you will be able to make a ton of money from them without getting offended. If you do get offended, try not to show it, - you need their money.