Eliott Carter was an American composer, whose personal harmonic and rhythmic language led to the invention of the term metric modulation. The latter describes frequent, precise tempo changes. In David Schiff's book "The Music of Elliott Carter", it is written that Elliott Carter preferred to call it tempo modulation.
Answer:
Be polite.
Explanation:
As the saying goes, kill them with kindness. If someone is being impolite, either 1, look at the situation i their shoes. Or 2, just simply keep on your professional face, don't lash out, don't act with hidden violence (Etc; slamming money on the counter for them to grab) Just simply apologize and continue working. You're only there for money, or to just have fun, or any reason at all. There's no need to have one person ruin you're mood.