If you were at school and hadn't done your homework, even though you knew what you should have done and you'd had a week to get it in, you would still have to go to class. Stand up, be counted and move on. I'm jumping ship from CD and cannot stress enough the importance of drinking water to flush the system to get rid of toxins.
Whilst its hard on the day of WI, it is important to keep going. I've just started Zumba and on week 2 was desperately trying to find a reason not to go (especially as my friend couldn't make it) but forced my self to go along and actually thoroughly enjoyed it.
Good Luck
M x