How do you stop yourself from being stressed at work?

I let myself get very stressed at work, I work drive ups and can't help but over stress myself juggling orders trying to hit them in under 3 minutes, or at times just get them out at all because the parking lots filling up

I worry and stress and its physically hurts my body, I have been doing drive ups since they invented it and I feel like I'm expected to do the jobs of multiple people, I'm the opener and when people call out they mostly ignore it and wait for the closing/afternoon people to come in near the end of my shift because they know I'll juggle multiple orders running around but I can't just stop trying either

Last week I worked 4 days in a row by myself opening and the stress I felt was insane

I know logically I should not care so much, if the parking lot gets backed up or the orders are late it just is what it is- but I can't help it my heart starts racing as I try and dig myself out of it. What should I do, or what do you do do stay calm under the pressure of work while its happening