It’s all too obvious when you’re tired—your behavior changes so drastically. I can’t exactly fault you for that, as that’s natural for anyone who hasn’t slept enough. Recognize, however, when you’re in these states and do something to combat the slowing of your productivity.
It may seem like a valid solution to “power through” and remain tired for the entirety of the day, but you’ve experienced firsthand the lousy results of an approach like that. You’re still tired, less focused, more emotional, less reasoned. If you would take 12–15 minutes to relax, rest your eyes, and not think, the rest of your day that would go smoothly.