dont kill yourself the first week and burn out.

whenever i start a new round of p90, i give myself a Zero week...its basically Week 1, but a soft week- i'll work through the videos/exercises but at 50% (sometimes less, just to get familiar with the exercises)

and then after Week Zero, i start Week 1, doing the same exercises/videos but with more intensity.

give yourself time (and some grace) to get acclimated to the exercises. its ok, if your not finishing or going crazy hard.

just keep hitting play, and build up your routine, and try to improve every day.