you might be overtraining, take a week or two off and eat only twinkies and donuts and then go back and hit the right diet and weights and you will have a renewed level of commitment and intesity. and you will not want twinkies nor donuts for awhile.
There will always be some times when you can't be bothered or don't feel like it, but I try to just ignore them. This usually only happens every now and again when it puring with rain and I can't be bothered to get out of bed and always goes away when I get to the gym.
When I hit the I HATE WORKING OUT days I take my body to the gym and hope that my mind follows. But sometimes its ok to take a few days to recover. Or may be you are deppressed because you are going to Cancun Ha! Ha! Ha! just kidding.