“Shit happens” the elegant saying goes, and it’s true. You’re going to make mistakes, and that’s fine. You’re human. You may even make big mistakes.
A common way in which work relationships are sabotaged is because, once you make a mistake, it takes on a greater importance in your mind than it deserves. If it is a “small” mistake, in your mind you treat it like a “big” mistake. Even if it is a “big” mistake, you treat it like a “huge” mistake. Even if it is a “huge” mistake, you treat it like a world-changing nuclear bomb of a mistake.
Once you’ve upped the importance of the mistake in your mind, then, suddenly, because it’s so important (in your mind) it becomes incredibly hard to get over it. You freeze when faced with future decisions. You feel a compulsive need to quintuple check everything even when you really should only be double or perhaps triple checking everything. You feel an enormous burden on your shoulders. The guilt gets to you, wasting brain cycles and emotional cycles, preventing you from doing the job as well as you need to, and ultimately sabotaging your work as your performance wanes.
The best way around this is to realize that however important this is to you, and no matter how angry your manager may be at you—it’s much, much, much less important for your manager or the company than it is for you. (Unless you literally dropped a nuclear bomb on the company, but let’s assume you didn’t do that. If so, I’m not sure I can be of any more help to you.) You may think that your mistake will end the company but from your boss’s point of view? He’s managing 11 people and you’re just 1 of them so that’s 9% of his management energy. He’s also managing budgets and clients and vendors and much more so that 9% of his energy that’s focused on you is more like 3% or less. For you, it’s the big fire, but for him, it’s just one of dozens of fires every day.
As a result, whatever the issue is, it is much, much, much less important for the boss and the company than you think it is, nuclear bomb aside. Therefore, the importance in your mind magnifies it too much. So, calm down about it. And remember what is most valuable is your energy and time, and if your energy is going towards reliving a mistake, you just can’t get over it. So, do what you can to try to minimize the importance of the mistake, internalize the fact that it is minor in the scheme of things for the company, and focus on the next mission. While, of course, learning the lessons so you don’t make the same mistake again—and letting your boss or client know that you’ve learned from it.