Whereever there are humans....
Wherever there are humans.... there's the potential for human error....
I try to minimize my potential for making a mistake I could regret the rest of my life, by keeping things as simple as possible.
Of course, the simplest way to avoid this kind of mistake is to keep everything locked up in the vault. But to me these decisions usually come down to risk management, and (imho) in this sin sick world we live in, choosing not to carry is far from the "safest" option.
So here's a couple of my KISS principles...
1. Concealed is as concealed does: Keep your business to yourself! (This is really hard for some people to do.) If you walk into the P.O. to ship your package and forget that you're armed, just keep you cool and go about your business.
2. Loose lips sink ships: Don't advertise that you carry, as you're just going to make problems for yourself. People have a unpredictable habit of saying stupid things ("hey buddy, are you packing?") and often do so in front of the wrong people. People also have a nasty habit of being two faced and talking about others behind their back. You don't want your 'concealed' carry choices to be the topic of gossip at the coffee mess. I work at a company that, despite the owners being hunters and mostly conservative thinkers, bans firearms in the work place. Yet, for reasons that are my own, I've both intentionally and 'accidentally' carried at work. Once I was called into an impromptu meeting with all the dept. heads and the owners while doing so. Because I stay off the 'radar screen' of others, this has never been a problem. And as far as bragging and showing off go... aren't these the fruit of insecurities we're supposed to outgrow?
3. It's all about procedures: Develop a personal manual of arms that is deliberately un-complicated, then deploy it consistently. Sound, well established habits, can save your butt. And the more complicated "if then" your procedures are, the more likely you are to forget what you did five minutes ago. Did I chamber a round? Did I clear the chamber? Is the trigger lock on? Is my car locked? Not for me! I know the answer to these questions all day every day, because I do it the same way all day every day. And if some odd circumstance requires me to change my routine.... it's going to seem unnatural enough to keep my mind alert.
4. Ignorance is NOT bliss: Know the law in your state and town were you live. Know the law in the state and town where you work. Don't get your legal advise from Internet bulletin boards. Know how your firearms function. Know the four rules cold. Know the written policies at your place of employment. Know Federal laws concerning firearms. Know UPS, FedEx and USPS rules for shipping firearms and ammo (which are often based on Federal laws).
If you can do all of this on a consistent basis, you'll keep Murphy's Raiders at bay, and improve the odds that you never have an 'incident'. At least, not one that 'goes public'.