If there is a common pitfall, it's the one of being too ambitious.
Other than that, I guess the important thing to realize is that developing a game is just like any other job - it's hard work. People tend to think that since playing games is fun, building should be fun too, but it is in fact 95% work. Which primarily means you need oodles of tenacity and (to make this easy on yourself), always work in small increments (my biggest mistake).
Once I finish Imperium, I think the only projects I'll work on (absent someone handing me a big pile of money to do the work, of course
), will be small projects that I think I can finish in six months or so (<- which means they'll probably take about a year or more
).
