P90X is a 90-day at home fitness program. The program advertises itself as an extreme program, so if you're tired, you may struggle to do it. Just try to do your best. If you're dead tired or sick, don't beat yourself up if you need to skip the occasional workout. Follow your gut feelings.
Fuel Your Workout
If you're tired, you might simply be hungry. Prepare for your workout by fueling your body. According to registered dietitian, Nancy Clark, "The best pre-exercise snacks digest easily, settle well in your stomach, and do not talk back to you." Clark recommends a carbohydrate-rich snack such as bananas and yogurt or pretzels and raisins to give you the energy you need to get through your workout. You can also use energy bars or sports drinks to fuel your workout. According to Clark, a bit of caffeine combined with carbohydrates can enhance your performance and make your workout easier. Have some water, too.
Do Your Best
Tony Horton, the creator and host of P90X, recommends simply putting the DVD on and doing the workout anyway. But if you're really tired, you need to be prepared for the fact that you are not going to have a perfect workout. According to Horton, "You must be OK with the fact you will be weak and puny and rotten at it. Any workout, no matter how bad it is, is always better than NO workout at all." Keep that in mind and simply aim to do your best.
Shift Your Rest Day
The P90X program calls for one rest day per week. Normally, you take your rest day on a set day of the week, but it's okay to move your schedule around a bit as needed. For instance, if you're scheduled to take your rest day on Saturday, there's no reason you can't take it on another day of the week if you are tired or not feeling well. Just adjust your workout schedule for the rest of the week accordingly.
Extra Rest Days
According to the P90X Fitness Guide, it's alright to take an additional rest day if you need it. You don't want to skip workouts on a regular basis, but if you're especially tired, or sick, taking a day off can help you recover properly and come back stronger. According to Horton, you should simply pick up where you left off. Doing this means that you'll need more than 90 days to complete the program, but it won't hamper your progress.