Well, the Lost Cartridge Jam 2022 just finished this weekend, and I just managed to submit my entry (Goblinoid, this game) with about two hours to spare before the end of submissions. 
I had gone into the game jam with the goal of creating a fully playable game with a minimum of 25 levels as opposed to submitting a partial game, proof of concept, demo or short. Due to my experience with previous projects and participating in several game jams over the years (making smaller projects), I was confident that I would be able to pull this off in 72 hours, with time to spare for some final polish.

I reached the goal of finishing a 25 level game, but as the time for end of submissions came closer, I was scrambling to even get that done in time. I quickly realized that once there was a definite deadline that my previous approach to (relatively) larger projects went completely out of the window. 

Even laying out my timeline for doing specific things wasn't going according to plan, due to a power outage and frustrating bugs. As the deadline was steadily approaching, my thoughts of adding that extra polish just wasn't an option anymore.
Unforeseen circumstances could pop up at any moment, and if these eventualities aren't factored into your timeline for development, things could go horribly wrong.

I realized that the scope of my idea was definitely doable, but at a cost. I managed to reach my goal, to a degree, but with time running out, and without extensive testing, several little things slipped through the cracks, some which are there out of necessity, others which I only caught after the game was submitted. Things like:

- Really ugly main menu, win and game over screens. And an absolutely horrible help page with typos which cause bad grammar and makes it seem that I don't speak English very well.
- Some really weird behavior when you manage to both run into a trap and catch the final Bloofing in a level, causing you to lose a life, go to the next level, then after a few seconds restarting that same level.
- Extremely erratic difficulty scaling from level to level, even more so in later levels, as I was sacrificing game balance for just getting 25 levels done and dusted.
- To make the levels less bland, I created a bunch of 'decoration' tiles to make the levels a bit more visually appealing, and less monotonous. However, after release, I realized that I had missed adding these tiles in 3 levels of the Caves area altogether, and on a few levels there are a few incomplete decorations missing some tiles.
- Several problems with the game icon sometimes reverting to the default Godot icon for no apparent reason.

I'm sure that there are more bugs and oddities I may have missed, and I urge anybody who finds anything weird or broken while playing to let me know so I can address them in a later version of the game, once the game jam judging is complete.

What have I learned from all this?
Well, I can now more safely gauge the actual scope of projects I can do within this time limit, and plan on adjusting things accordingly for future jams. 
Also, working possible unforeseen problems which may hamper development time into my schedule will also make things more manageable in the end.

Overall, it was a fun (if at times frantic) exercise, and I'm looking forward to more future Itch game jams.

Best of luck to all entrants of the Lost Cartridge Jam. I must say that I have seen some really amazing entries this year.