What worked for me back when I shopped at Walmart was to go early - like 7am. I went calling my wife to help talk me down from taking a swing at someone, to in-and-out in a half-hour with a cartload of stuff and no stress. Walmart sucks for anything like produce or meat, but so long as the store is relatively convenient and a person has the choice of when to go, why pay 2x for the same cart of packaged commercial goods?
And a more comprehensive solution is to stop being an elitist douchebag.
I'm still working on that one, but that helped my attitude at Walmart or the gas station counter more than changing shopping times