HOW TO DEAL WITH MAKING A BIG MISTAKE AT WORK.
Everyone makes mistakes on the job. If the mistake is large enough, your job or reputation may be on the line. Most mistakes surface whether or not you own up to them. If you don’t own up to your mistakes before your supervisor becomes aware of them, then those errors will look much worse!
Breath, chin up: Be straightforward, as soon as possible. Make it clear you understand the seriousness of the mistake and that you’re mortified it happened. Explain briefly and without defensiveness where you went wrong & what steps you’re taking to avoid it happening again.
You may have to regain your boss’s trust. Worst-case scenario, she may have real doubts about your fit for the role. However, you’ve dealt with it and lesson’s were learned.