Mind over matter, or is it nore than that?

Yesterday and today I have had the hardest time getting up to work out.

Today, I woke up at 6am. That is a great time to get going and work out. In fact, for a while (2weeks) I had a great routine of getting up, eating a yogurt, drinking some water and hopping on the elliptical to get my workout over with. I get off, stretch, do some sit-ups and other toning exercises while keeping my heart rate up and I'm done before my kids get up and their demands start. I felt great. I loved that routine.

But back to today, I'm awake, my body says lets go, get up, workout. My brain says no, bed is warm, cozy, nice.

Why does my brain win?

I'm going to work out anyway. Why do I torture myself and not get up at 6am since I am awake anyway? I know I feel GREAT when it's over.

Is my body needing something nutrition wise? Is something I'm eating chemically clashing with my motivation/brain? How can I stop fighting with my brain?