It's perfectly natural to want to walk into work and start shooting. If you don't ever think about it, then you're probably not paying attention...And likely will be one of the people shot...
But you know that what you need to do instead is take a deep breath, and find a way to move forward. When a moron stands between you and doing the right thing, then consider your course of action. Can you go around him? Above, below, or through?
The trick is finding the equanimity to take the tack that not only solves your problem, but actually makes it easier for the next would-be postal worker to come along. Believe me, you're not alone. And neither snow nor rain, nor heat nor gloom of night will stay us from the swift completion of our appointed rounds. Let's just try to not hurt too many morons in the process.