mid afternoon slump

I'm on my afternoon break and I feel like I could just put my head on my desk and go to sleep. I guess it's because I had a lot of carbs for lunch and my sugar high is subsiding. I really need to get back on my diet. I hate feeling like this. I feel bad partly for eating something that's not "approved" but mostly just physically feeling yucky because of what I ate. I resolve to start this evening. I am going to start eating better again.