Here's one rule that makes me happier and that, I'm sure, will make you happier, too: when a firm is doing something you don't understand, give them the benefit of the doubt. Firms have lots and lots of money on the line, and while they make lots and lots of mistakes, they probably have at least a plausible reason for doing what they're doing.
Consider airlines. I've come to appreciate their practices more and more since I first earned Silver Medallion status with Delta in 2010 and started getting occasional upgrades to first class, preferred boarding, and other niceties. I will periodically hear people get frustrated with how airlines load and unload planes, their fare schedules, and all sorts of other things. I've come to appreciate just how finely airlines tailor their practices to the preferences of consumers so as to get pretty much the maximum consumers are willing to pay for the levels of service and comfort they want. Southwest Airlines has a great business model for people who like no-frills travel, and I've always been a big fan of Southwest. Since earning status with Delta--and I pretty much had to specialize in Delta and US Airways while I lived in Memphis because SWA didn't serve Memphis--I've come to appreciate the differences between the discounters and the large airlines.
To use just one example, consider how airlines board by zone. Because I have Silver status, I'm always in Zone 1, which means I get to sit closer to the front of the plane and around other travelers who travel frequently enough to be able to get on and off flights pretty efficiently. Since I'm one of the first ones on the plane, I also pretty much always have room for my carry-on bag. The extra few minutes from getting off the plane earlier made a big difference a few months ago: I was able to get home earlier because I caught an earlier connecting flight to Birmingham just before it closed.
I hope to write a lot more in the coming months about mental habits I've picked up that I use to lash myself to the proverbial mast. One of those habits has been to recognize that people (and firms) face different trade-offs than I do. Might they want to be a little more transparent about the levels of service for which people are paying? Perhaps: I chatted with a flight attendant once who expressed annoyance at belligerent passengers who expected first-class service for coach-class fares. I'm a lot happier, though, since I started asking (and trying seriously to figure out) how a particular policy or practice makes sense when I encounter people or firms doing something or enforcing a policy I don't understand at first.