I break these things down into bits, it helps when I feel like I'm just trudging along and don't feel like doing anything. I always try to do at least one thing per day - say like all the mountains on one island, or all the trees, or all the rivers, etc. That way I at least make some sort of progress and don't waste a lot of time either for when I want to spend that time on other things like sleeping. I'll spend an hour or at most 2 and I still have time for other things. Compartmentalizing helps me very much.