Besides all good advises above, it’s better to have a group of like-minded people doing P90X too. That’s one reason BB promotes a system of coaches and private Facebook groups. It doesn’t cost you anything additional, but sometimes provides necessary help and promotes engagement.
I finished my first P90X round in January. I’m almost 50, very active (mountain climber, trail runner) but never was involved with such extensive at-home exercises before. What was most difficult – to get up every morning and did a whole hour of exercises before going to work. After work I did other things, climbed, swam, etc. So, some encouragement from a private Fb group helped too.
Results were just great! I’m now in such a shape I never was for last 25 or so years. Switched to other wonderful things – TRX Suspension Training, Kettlebells, etc. Non would be possible without initial conditioning by P90X.
Running ultra-marathons became much easier too.
If you don’t yet have such a group and a coach, I welcome you to participate in my group (I was crazy enough to sign up as a coach recently).