"Tell me about a time you aimed too high."
This is another question where you can turn this answer into a good experience. I am going to be using the answer as the one where you failed to complete an assignment on time. This is good practice to use a similar answer by changing only a few sentences to answer another tough interview question. But first, I'll give an example of a different short answer.
Short Answer
"We had a new project that I was interested in. Even though I was busy, I volunteered to take on the assignment. I had to work so much more. Although I managed to complete the assignment, it really burned me out. I feel I aimed too high and I would have benefited by doing a better job on my current assignments instead of wanting more challenges."
Long Answer
"I believe aiming high is a good practice. Aiming high keeps me focused and forces me to grow by trying to reach high goals I have set for myself. But I know there are times where aiming too high is not good. For example, one time in the middle of the project, our clients wanted to change one aspect of the assignment that we already completed. I analyzed the change request and told them that we will not be able to make the date. I estimated that it will take three additional days. They insisted that we finish on the agreed upon time schedule. I told them we would try but we could not promise anything. Even with hard work and overtime, we missed the due date. We did however, finish one day later. I challenged myself to complete on time, but with the large change request, it was too high of a goal to reach. In this case, I really aimed too high. I should have been more firm telling them that we will need a few more days."
This is a similar experience we already used, but you changed the beginning and the end to tailor it to this question. Remember that you can use one answer for multiple questions. This answer should make you look good instead of looking like you made a terrible mistake.