Start fun and small. Do the fun stuff first, get your mind obsessing over it (sketching up your mockups, database schemas, etc), so that that's all you're thinking about, then starting the coding isn't so much of a hassle. Don't think too big off the bat, or the project will seem too daunting. Focus on getting a small prototype up and running, then once you've got that momentum, you can start adding features.
They say to start but not finish the easy stuff at night so that when you wake up the next morning, you have the easy part to finish, which gets you started. Then, once you've got momentum, continuing on the harder stuff is easier.