By the early-afternoon hours, if your brain is normal, it's running strictly on inertia and reflex. All you can do during those hours are the things that are exactly like other things you've done in similar situations. Creativity is out of the question. You might argue that you don't notice any difference in your thinking during the afternoon. That's because you're too dazed to notice anything during those hours. I'm sure it's true for me; I believe you could set my eyebrows on fire during the afternoon and I wouldn't notice until sometime the next morning.

The Joy of Work: Dilbert's Guide to Finding Happiness at the Expense of Your Co-Workers