Joy versus misery

I am very fortunate to work in a job where the huge majority of customers are friendly and appreciative of what I do for them. Maybe once a week there will come along a miserable soul, who wants to make me miserable, too. When I first was hired to do the job, I would let that person ruin my next hour or too. Not any more. Now I recognize right away that this person's misery is the result of choices he/she is making. I do not have to get sucked in to his/her misery. Not even for a few seconds.