That’s how I am with every jam I participate in too: overscope and wind up with unfinished projects.
The best way I’ve found out to avoid that is plan your project to be finished in 1/3rd the actual time you have.
Chances are the game will take twice as long as you expect it to,
The final 1/3rd of the time is great for playtesting, bug fixing, and maybe adding some extra polish.