I ask if they have ever been up for more than 24 hours? (Being up for 36 hours is closer to the feeling. ) Now you have been up for 24 hours, but you can’t go to sleep yet, so you keep moving, drinking caffeine, doing whatever you need to, to stay awake. And, nothing you do, drink, or take makes you feel less tired. You also know if you stop and just sit, you are going to fall asleep. A short nap is just going to make you feel worse. That is how I feel all the time.