I know what you mean, but do just the opposite - that's what I do anyway. Eat a lean mean green raw veggie meal, with seeds, nuts and fruit. Then go for a walk if you can and get some sun - you've got to be like a salmon and swim upstream against the currents to get where you want to be. Don't give in the the lethargic-ness that is tempting you, fight it with all you have.
Peace~
I have heard this before in articles...why? If my body wants to rest why should i fight it? Maybe it needs rest?