Have you ever worked on a project that had a tight-but-achievable deadline, and that needed your unique, expert knowledge for it to be completed successfully? Even though you found it challenging, you may have delivered some of your best work. Or, think back to a project you worked on where there was little pressure to deliver. The deadline was flexible and the work wasn't challenging. You may have done an average job, at best.
Discuss why you think this is? What made the difference in producing the best work?
Can't change a rubric once you've started using it.