There are ways to resist this.
1. Sit up. Get a bunch of pillows or something to prop you up almost 90 degrees. Don't slouch, it's bad for your back. Helps keep you more awake. Personally, I have a pillow with armrests. Look around for one, though it's hard to describe. I believe it's called a "husband."
2. Drink something cold or hot. Something that will keep you up. A cold soft drink will be cold enough not to make you drowsy, or some really hot coffee (not necessarily decaf)
3. Caffeine is your best friend. Or sugar, though I'd recommend caffeine; it's more potent. Not too much, though, can kill some brain cells. Remember, it takes 10 minutes to penetrate your brain.
4. Sleep aids. NO, I advise against them, they might have some side effects, besides, you could still fall asleep after lying down and taking them anyway. I have a better solution:
5. Bright light. A good 60-watt light-bulb aimed at your face, though not directly in your eyes, perhaps to the side. I find it a great way to stay up, though you might get drowsy, just don't close your eyes, not even resting them, you'll always fall asleep, and not get a great sleep because the light is on.