It is my first game jam and I didn't knew what to expect. The curve was basically: Having fun at start and more and more panic as the deadline started to get closer, which is no surprise. Last two days were worst and even that I normally sleep long, I was suddenly wake at 6AM and can't fall asleep as I was thinking about the game and all things I needed to cross out from the original scope. But it was totally worth it - it's such a great experience.
My two tips are probably these:
1) When you are stuck on something, switch to another task before you burn out. This applies more for solo devs, where you have to handle all the aspects of the game and you can switch between code, graphic and game design parts. And when you have nothing to switch to, just make a little break, go on walk or something.
2) Make a solid bandwidth before game jam end to check everything works with your exported game. There are some things that might work in debug, but can ruin all your effords in production.