"I am a very focused individual as it is, so it isn't very difficult for me to remain this way while I work. The busier I am, the better. If I feel that I am becoming unfocused, I will take a quick lap outside and then get back to work."

Interviewers want to figure out whether you enjoy the field and seem like someone who will stick with the profession long-term. If you seem like you care, you'll work harder and overcome challenges. If you don't seem to care at all, you're more likely to quit when things get tough, or just think of this as a job and not put in the extra effort when needed.