Dance/Ballet- awareness of needing to stretch

On Tuesday, this week, the 12th, I had ballet class from 6:30 to 8, and for some reason I felt way more tired than I usually do, and not stretched out whatsoever. And I really didn't want to stretch out and as a result, I wasn't stretched out enough for class. I think that maybe from now on, I should do at least a half hour of stretching before class, to be warmed up. Also I keep noticing that my feet are stronger and stronger each class.