I work as a cashier at a grocery store, and I often run self-check which has 10 registers (wish it only had 8 like it used to)
When I start to feel like it’s too much, I sometimes scan the room, at a slow to medium pace, for example, I might give 2 to 4 seconds of casual visual attention to this customer, 2 to 4 seconds of casual, low-key attention to the next customer, and so on. This helps to calm me, and also helps me to appear calm and in control, which is important in a public job.