The key to changing your response is to get some insight into what triggers your rage. And one clue to understanding what's going on here is your helpful admission that you react even more strongly to the small stuff. My best guess: You're projecting onto others an intolerance you have for anything less than perfection in yourself. You then respond with the same punitive attitude you may have toward yourself when you make mistakes on something you consider simple--errors you think there's no excuse for.
Because of this harshness, which you may have learned the hard way by being on the receiving end of it in childhood, you also appear to have developed an over-inclusive definition of "incompetence."
Don't you think there's a difference between making a mistake and being incompetent? In your eyes, it seems, errors exist on a continuum that leads to a global indictment of one's character. Intellectually, you might agree that to err is human, but emotionally you're unforgiving.IF THESE INSIGHTS make sense to you, try, after some reflection, to remind yourself of them the next time someone around you messes up. Holding your anger in check will take some deliberate self-restraint for a while, until greater self-awareness sinks in. But in time you should have more control over your responses as a more tolerant attitude, toward your own mistakes and those of others, starts to kick in automatically.
In the meantime, distancing yourself physically may help keep things cool. Don't hover or stay on the phone after pointing out an error; just make a plan to check back in with the subordinate, vendor, or colleague in question after the work is corrected. And if you do blow up, you might consider apologizing. Among other things, it may produce an unexpected payoff: fewer errors. People who are intimidated by anger, after all, are probably more likely to make mistakes. Kerry J. Sulkowicz, M.D., a psychoanalyst and founder of the Boswell Group, advises executives on psychological aspects of business. Send him questions at firstname.lastname@example.org