When I have to choose a line I find myself harshly judging the people around me, because every difference can impose a cost in boredom and lost leisure time. "This guy's old and worn out. They seem kind of foreign, won't understand the cashier. That one looks poor, probably uses a lot of coupons and argues about what's discounted. They're paying all their attention to their kid instead of getting out of everyone's way." It may be the most socially corrosive thing I routinely do.

Edit: and I think I just convinced myself to get a smartphone (I'm reluctant to bring a paperback, it might look like shoplifting because they sell those).