The thing that I've learned is that you should do as many sessions as you'd like.
If you're tired, hungry- just go do something about it. Even if your head is empty, stand up - look out the window, refresh yourself.
Don't put finishing the game as priority.
When actually making the game I usually put gameplay first. That will make game breaking bugs show earlier and more possible to fix.
I can always change placeholder sprites and sounds, but entire scripts are kind of set in stone.
"Whether you finished or not, I think the fact that you showed up and tried is what counts."
That reminds me of my first game jam. It was about diving.
I spent so much time on the diver and water fading to darkness effects that I never did any fish. Eventually I just made it a swimming simulator and made text scroll by explaining how I'm still proud of what I made, even though it barely fit the theme with no gameplay. Uploaded it anyway, I think that's also important.