Really fun idea! Don't be so hard on yourself! Everyone started omewhere!
e.g. I used to not feel confident in the 3d models I made in Blender. I still have lots to improve. If you keep at it and learn more, making games will get easier!
Next time, you can re-use assets or code to make things easier. The rules say you can, (with conditions) so there's nothing wrong with that.
Also, maybe there's other game jams that give you more time, and that also allow re-using stuff.
Good luck!