Keep working on it. Fractal Terrains has a learning curve, so even if you don't finish this one, think of it as good practice. I haven't done much in it with hand-building my own worlds yet. I prefer randomly-generated worlds. And I quite often find myself starting over from scratch when I learn a new technique. Although starting over is much easier for randomly generated worlds. If you think there are times when you might want to step back and do parts over again, then I would suggest saving copies of the world at each major step. That way to go back all you have to do is open up an earlier file and continue from there.