Walmart is many things, and one of them is full of people. I'm very easily unnerved by large groups of strangers, so I've fallen into a few routines to make my shopping trips more comfortable.
The trick to not being decomposed by strangers is to be even stranger. Sure, I might be a bit uncomfortable when a family is blocking the aisle with their cart, but they're probably even more uneasy with the long-haired fellow perambulating up and down, reading the labels on mayonnaise jars and humming disjointedly.
It's not a perfect solution, or even a very good one, but I like to think that most people consider themselves normal, and seeing things from their point of view makes shopping much more interesting.