But many times, you will learn something on the way that you can recycle in a future project.
PS: if you don't tell anyone about your "failed" projects, this strategy will make you look like a genius.
So I learn very little, and often restart the same things over and over. Eventually I give up and play computer games because they steer the focus and drip-feed novelty and reward compared to actually doing anything more productive.
I've noticed my frustration tends to stem from a feeling of not progressing quickly enough, or getting bogged down in architectural details before strictly necessary and then abandoning the whole thing due to the assumption it's too complex for my knowledge level...
“I know everything, just not at the same time.” But for our most gifted engineers, it’s practically as if they know everything.