The two moments that come to mind for me are the first day and the last day.
When the theme was first announced I was at work, so I had to sneak over to the bathroom to check it out, and then I was chatting with a coworker about ideas for the game. We had discussed some of the possible themes the day before, but death was one we didn't have anything for lol. That lead me to the idea of needing to die to progress in the beginning of the game, and it all pieces together from there.
Fast forward to the last day. At this point I had made all the levels and mechanics the game needed, so my focus was on polishing what I can, and adding the narration. I figured this would be one of the easier days, so I hadn't started until after all the days errands. On top of the touch ups, I wound up also making 3 more levels, and adding an options menu. By the time I finished submitting it was 5am, and the feeling of delirious tiredness combined with the joy of finally putting out a game of my own while seeing the sun rise in my window is something I'll always carry with me. It'll always be my reminder of what's possible when giving a project your all.