How do you finish your games?

Maybe this is just me but I find myself stuck in a cycle where I'll get really excited about an idea, come up with mechanics and lore and abilities and stuff, start putting things together and then... just stop. It's not a motivation thing, I WANT to finish these games, I'm excited about it, I've even done some of the art myself, and I KNOW what I need to do next, whether that's playtesting or writing or just putting everything together, but for some reason, I just can't bring myself to finish. Is this just me, or do you guys have any advice?