Great retrospect!!
This is my first game jam too so I would like to share my story as well.
Just like you I went into the jam maintaining a decent enough sleeping and eating schedule(Roughly 6hrs sleep and 2hrs breaks). I solo developed my game using unreal engine from scratch which I think was a big mistake. I was completely off the mark as to how long it takes just to implement the basic structure of the game (like character movement and such). Just this much too almost the entirety of the first day. Now knowing fully well, my lack of knowledge in texture and asset importing and the general random unreal engine behavior I was determined to import and check out all the assets b4 I go to sleep. Now is when I realized that I should have given more time for this task as all the assets either were discoloured (for some reason the hue was totally off) which I had to fix manually one by one and all the assets were way too freaking small compared to my environment.
Day 2 was a hell scape. Assets were showing random visual anomalies (which had to do something with me placing them real close or something :D). I still hadn't implement any of the levels, hadn't implemented any of the gameplay mechanics and didn't have the time to implement a main menu screen. So I did what i do best and yolod it. Made a level named main menu with instruction spread throughout as floating texts. Made 3 levels and duplicated them so that I can make a one way flow instead of having to do a complex loop. Copy pasted some blueprint logic I knew I couldn't conjure up in time and then went on to build the project. The final result is playable enough I guess but I missed a lot of obscure places where I should have had instructions for. But hey they game atleast looks hella impressive for something I did in 2days!(Proud of myself)
Overall should have not implement everything from scratch. 5/10 failure rate, could have been worse!
You can check out my game for yourself here!: https://itch.io/jam/kenney-jam-2023/rate/2184146
:D