You're sitting at your desk mid-afternoon with that familiar fog settling in. The spreadsheet in front of you might as well be written in another language. You got maybe four hours of sleep last night, possibly five if you count the hour you spent staring at the ceiling thinking about everything and nothing.
And now all you can think about is something sweet. Or salty. Preferably both.
You know you're not actually hungry. You ate lunch two hours ago. But the thought of a candy bar or a drive-through order won't leave you alone. It's louder than your logical brain trying to suggest an apple.
This isn't about being lazy or lacking discipline. When you're running on insufficient sleep, the parts of your brain responsible for complex decision-making actually become impaired, while the regions that respond to rewards and motivation get amplified.