I've got a couple ongoing personal projects too. Nearby places and themes I'm always interested in photographing. Challenging goals, lots of variables, and no deadline.
Not only does it kindle creativity, it builds perseverance and patience, knowing full well you'll either get nothing worthwhile or will be surprised with a wonderful gift, if you're ready.
I know a couple other photographers who go for regular (rote) walks, such as to walk their dog, and come back with wonderful different photos all the time.