Here is some additional advice from Vanguard's recruiters on how to answer this question. "Answering these types of questions with responses such as, 'I've never made a mistake,' isn't going to reflect as well. Everyone makes mistakes. If you are asked to describe an error of some kind, know that it doesn't have to be a major mistake. You can describe a miscommunication, a time you forgot to return an email, or when you misread a school assignment. Humility and the ability to correct your actions are good qualities to demonstrate."

"A while ago, I scheduled a meeting with a client in the same slot as another meeting. This was an important client as well, the meeting was important, and both were priorities. So I explained my mistake, and that I was eager to accommodate the client, and failed to verify if that time slot would work. So, my supervisor told me not to be too hard on myself and asked if I was going to do it again. I told them what I'd learned from it and assured them of the steps I would take from now on to ensure it wouldn't happen again. They then said the client should be accommodated and covered all the meeting points with me. They told me they would share the post-meeting notes with me as well afterward. My meeting with the client was a success as well. So all's well that ends well."