I've done a bunch of jams over the past year or so, and what I've learned is that repetition is your best takeaway from every game you make, good or bad. You make a game, you learn a bunch of stuff to get it to work, and you forget 80% of it. Then you make another game, and you're able to do a bit more because you still have that 20% in your pocket to build on. So you learn more, forget most of it, repeat. But each time you're starting from a better and better place, and get to spend more time on more interesting mechanics, ideas, etc. And feedback from the community can boost you even further!
Never be upset you made a bad game. Be proud you made a game.