Focus on a particular time you felt unhappy with your work. Talk about what made you feel disappointed with yourself and how you were able to turn things around to recover from this disappointment.

"A few months ago, I sent an email to a client by mistake. The email was meant for my coworker, and although it was not an unprofessional email, I was disappointed in myself for being careless and not checking the addressee before sending it. I felt that it made me look incapable. I apologized to my client, and he was very understanding, but I always double-check now."