What I’ve found most important when working on a large project is keeping it small. To quote Antoine de Saint-Exupéry “What saves a man is to take a step. Then another step. It is always the same step, but you have to take it.” Along with the project you are building, you are also building habits. It’s those habits that will determine whether your project reaches fruition or decays in your memory. If you think of that great game you love as a sort of “accident”, there are plenty of designers out there who will prove you wrong. It’s their habits that have been able to produce great games again and again. So, develop a schedule and stick to it. Work on little bits of your game every day and you’ll see how the game takes shape.