About exercise in general (I've seen the PX90 ads on the net but never done it myself). I really think that it is important that you do move. How you move is not really the big deal. The main thing is finding something that does not become a grind for you, something that does not feel like WORK. If exercise stops being fun and exciting but you power through it anyway to meet some set schedule you feel you HAVE to do, then it's time to chill and take a day off.
If you are having fun with your PX90, cool. I really like Mark's unstructured way of approaching exercise. I bang out a random unplanned set of push-ups on the counter while waiting for my tea to heat in the microwave.
As someone who used to be a dedicated gym rat in my younger years and even into bodybuilding, I can say that the most liberating thing about PB was the day I cancelled my gym membership and walked away (down to the beach to do some sprints! For free!) This is fun.
Don't lose sight of the fun in all your diligent efforts.
BTW, that loin roast looks wonderful.