People in the workplace make mistakes all the time, but it is important that you learn to deal with them in an appropriate and timely manner. I would also make sure that you always learn from your mistakes, as this is something that I learned that employers truly do appreciate. If it is something that prevents you from going forward with a particular task, I would be honest with your employer and let them know the mistake, as they will appreciate you going to them and giving them a status of where you may be with something. The first step I would take is to try and figure out the best solution to the problem, if possible. Going to your employer with a mistake and a possible solution is a great way to show your employer your understanding of the task. If you are unsure of how to fix the issue, I would confirm with your employer why certain alternatives may not work. As an employee, it is your job to be honest with whomever you are working for when something goes wrong. Overall, maintain confidence and let your employer know that you will make sure that you will not make that same mistake again.