Bad answer:

I was most satisfied when I did well and got praised for my work.

Do not give vague answers. Instead, think about something you did well and enjoyed that will be relevant at this new job. This is an opportunity for you to share your interests, prove that you are a great fit for the job and showcase your enthusiasm.

Good answer:

I am a people person. I was always happiest and most satisfied when I was interacting with community residents, making sure I was able to meet their needs and giving them the best possible comfort in a tough situation. It was my favorite part of the job, and it showed. Part of the reason I am interested in this job is that I know I would have even more interaction with the public, on an even more critical level.