Michael Labbe has written an article about how to finish a full game. A majority of hobbyist tend to start on project and never finish it. According to the author, "the majority of hobbyist games never reach a completed state. Some may be playable, but most are not. Even if the author had the best intentions going in, the games never even reach beta status most of the time. This article takes a look at how to choose an achievable scope and examines the hobbyist game developer's most common pitfalls."
The article can be found here