Some introspection is always great to do before a medical school MMI. Remember that your evaluator at this MMI station will appreciate an open and honest approach, as long as you can reiterate that you know you can't magically change the quality you talk about. Instead, discussing how you have the self-awareness to work on it will pay dividends as your answer.

"If this magic power were to somehow make its way to me, I would honestly have to say that I would give myself the innate ability to set personal boundaries regarding my work. I have always been a go-getter in my school work and the jobs I have held and never held back from picking up extra shifts or projects. I also never hesitate to lend a helping hand to a student colleague or a coworker. Has this potentially hurt some personal relationships I've had and maybe even hurt myself at times? It sure has. While I don't see this quality as a negative during medical school, I certainly know it would in my future as a physician. And even though I do not have this magic wand, this is one piece of my personality that I have made it a point to work on. I know the next four years will be the most trying of my life, so taking time to unwind and relax at times will be vital. In that same vein, I look forward to having some great times with my class during medical school, where we'll explore the city, volunteer, and cheer on the local sports teams."

Identifying one thing that you would change about your personality can be a difficult task, but consider your answer a chance to discuss one of your weaknesses and stress it is something you are trying to improve upon. By taking an honest approach here, your written answer will show your genuineness to the team evaluating it and comparing it to other medical school applicants.