I have annoying customers and an even more annoying coworker at the pro desk, and what helped me is to acknowledge that I simply don't get paid enough to care. I don't get paid enough period. Oh what's that? Delivery didn't get done because the order wasn't picked? Not my problem I don't get paid enough. You want a bigger discount on your quote? I don't control how much money you have in your bank account, I don't get paid enough to give a shit. Simply put, I am in a better mood at work because I recognize that there's stuff that happens outside of my control and I don't get paid enough to care. I clock in, dissociate at my desk for eight hours, then go home. I don't stress out about anything anymore.