I had horrible day at work today!

I went to work at 11:30 this morning and my day started to get busy doing my job.Customers got left and right questions and blah..blah..blah! Suddenly a “rude” old man showed up in my face and started calling me as a dog. He commanded crudely to write his product number on his food. As and escape of his laziness, he told me that he is left-handed and can’t write because his left arm is broken! I almost told him “good for you, maybe He punishes you for you are rude”! The good thing is, I can still hold my breath even though I was about to explode! I just really hate rude a customers, they think I am their made but I’m not! I am working decently and not to be treated like a dog. I am a human who needs a little respect for my feelings too! I wish they'll change their attitude