Kenpo didn't happen today. I took the day off to go to the zoo with the family and one activity led to another and the day finally ran out of steam with the only time to do the workout being right before bed.
I would probably not miss a resistance workout. But Kenpo...well, its easy. It doesn't really build anything except a little coordination and balance. It burns about 700 calories, but I'm not looking to lose weight and I don't imagine I'll lose much cardio capacity by missing a day.
Besides, I am starting to think of the P90X workouts as being integrated into an everyday fitness routine...not just 90 days that reach some arbitrary goal. I'll be continuing this indefinitely, so I'm not going to beat myself up about missing one day.
So far I've missed one stretch routine in week 8 and now one cardio routine in week 11. I actually probably would have made this up if I hadn't pushed Legs/Back off one day and ended up with no extra day to play with.