For me, it is don't be afraid to make messy codes (in my case is spagetthi blueprint as I'm using Unreal) as long as it works. Then polish it if you want to take this project further.
Oh I'm definitely on the other side here. During jams I usually throw clean code out the window in favor of speed, which I did this time too, but by the end of this jam I really regretted it. The code became super spaghetti and slowed things waaaaaay down, so much dumb debugging that could've been prevented. For me the biggest takeaway from this jam is to assess if a refactor is worth it or not, rather than just charging forward with messy code. Not to say that allowing for some mess isn't ideal during jams, but there are a few core systems in our game that in hindsight should've been refactored right away.