[Chris]

I always recommend staying on schedule with your workouts unless you have a physical problem or sickness. Basically the way I look at it, being tired is an excuse. If you make an exception for being tired, then maybe next week you make another one cause you "don't have time", or "your training partner isn't available", or "you just don't feel like it today". That is a slippery slope, and usually once you make an exception, you are more likely to make another one. You can always overcome being tired, especially if its just for an hour workout.