As a cashier, you'll have your fair share of bad encounters with customers, so developing a thick skin is almost a primary survival method for this position.
Train yourself not to shrink from difficult situations and let go of fear. Most of the time, customers aren't mad at you or your professional skills but rather about a specific problem.
What about learning how to never argue with customers with a less than 2-minute video? Click here: https://www.youtube.com/watch?v=Z9uC8aF-RCw.
Source: Vendhq, 2021.
Photo by Helena Lopes on Unsplash.