Banish Fat Boot Metabolism Jillian Michaels - help!

Ufff. Okay - I thought I was reasonably fit before getting this DVD. Now I'm so demotivated. I often do Zumba DVDs and can happily do the 50 minute Live one followed by one of the 20 minutes DVDs. Now, I'm struggling to do 20 minutes of Jillian Michael's Banish Fat Boost Metabolism DVD (which is 50 minutes long). I actually spend about double the time getting 20 minutes done because of all the breaks I have to take.
Anyone else having trouble getting into this DVD? All the reviews on Amazon talk about it being hard but that it is possible to get through it after a few goes at it. I've been doing it for a month and I still can't get past 20 minutes with multiple breaks - which you aren't even supposed to take.
Feeling a little demotivated about it all. Perhaps I should go back to Zumba - but I feel I've reached a plateau with that and it just isn't hard enough. Jillian seems way too hard!