Lately I've learned to work with an iterative mindset. Instead of fully implementing each feature right away, I do all of it in a quick 'n dirty way, sometimes not even in a game engine but in something like PowerPoint if possible. Just to see if my idea has any potential. I understand that it's not something you necessarily do consciously, but try to avoid going for a 'full' implementation right away and just embrace the raw spaghett.