Yeah everyone is super different, and it is kinda funny to see all the varied replies here.
Some of the stories I hold onto when I'm having a tough time finishing are those of writers who talk about what a struggle it is to write. Jerry Seinfeld on the Tim Ferriss show was one of my favorite interviews ever. He talks about about how his advice to young comedians is to just work. There's no way around it. That's been a great comfort to me. The War of Art is another good source of inspiration.
I don't know what your goals are when you start projects; personally, I seldom start projects just for fun. If it's a program, then it's a tool I want to use. If it's project around the house, it's probably a repair or upgrade that has meaningful impact on my life. It's easy to get discouraged on these kinds of projects, but you have to see them through or in some sense you suffer for it.
In the middle ground there are things you kind of started because you wanted to, to see if you could do it, or because you thought it would be cool. Maybe a drawing you you were working on, or a research project (actually, I don't know if this fits or not). In a home wood shop, maybe you're making an new tool because you enjoy owning nicer tools than you can afford or just tools you made yourself. These projects, you don't really have to finish, but you probably don't want a graveyard full of them either. It's a pride thing. I start projects like this myself on occasion; they end up particularly hard to finish because I have too many of the first type.
Then there are people who are just screwing around, doing what's fun in the moment. I basically never do this, but a lot of people do. Those projects are fine as well, but people doing that sort of thing are going to have a very different outlook.
Some of the stories I hold onto when I'm having a tough time finishing are those of writers who talk about what a struggle it is to write. Jerry Seinfeld on the Tim Ferriss show was one of my favorite interviews ever. He talks about about how his advice to young comedians is to just work. There's no way around it. That's been a great comfort to me. The War of Art is another good source of inspiration.