For me, part of the solution is just keeping in mind that being pleasant with customers — even the ones I hate — is what I get paid for. Basically, I separate my feelings from my actions. I’m free to feel whatever way I want but, when I’m on the job, I’m being paid to behave in a certain way.
A couple of other thoughts that might help you. They’re lessons I had to learn the hard way!
1. The moment you allow someone else to make you react in anger, you’ve given them power over you, and they win. Don’t give them that power.
2. If you don’t like or respect the person, you have no reason to care about their opinion of you. So, there is no reason to feel hurt if they don’t like you, or if they insult you. Their insults are just meaningless noise that they’re making because they’re not strong or mature enough to take charge of their own emotions and behavior. When I have to deal with adults who get verbally aggressive, I see them as toddlers, because from the age of 5 on, humans have the developmental capacity to choose not to act on their emotions. So when I see an adult making a scene to try to change my behavior, they think they’re being intimidating, but in my mind they are simply behaving like a child of 4 years old. A four year old is not intimidating. And I’m not going to have any respect for an adult behaving like a four year old.
Thinking about your difficult customer in this way, might make you more confident in dealing with him, and that may reduce your stress in dealing with him.