If you've spent any length of time studying music composition, and you've studied with a few different instructors, at some point, you'll probably hear about the "gun on the wall" theory. It's not exactly a very scientific theory, but there is a good premise behind it. Basically, if you're watching a movie and you see a gun on the wall at some point this gun has to be used. Some of you might know this as the "Chekhov's Gun" principle. 

"Remove everything that has no relevance to the story. If you say in the first chapter that there is a rifle hanging on the wall, in the second or third chapter it absolutely must go off. If it's not going to be fired, it shouldn't be hanging there." —  Anton Chekhov

I was actually thinking about this theory while watching Super Bowl car commercials. Pondering how vehicles have advanced in the last several years brought me to begin thinking that the forward collision and automatic braking technology could be used to humorous effect in a new James Bond movie. Perhaps as he tries to run his enemies off the road, the car brakes and makes his task more difficult or maybe the car would simply just keep swerving out of the way to avoid a collision.

My point is that if I was making a movie and I introduced this concept of collision avoidance, I would have to use that information at some point. Of course, Chekhov was referring to the narrative in a play. In a dramatic production like that, you're going to want to avoid including any props that don't have a purpose. However, this theory also applies to composing music if taken with the right amount of flexibility.

Music is the same way. If you introduce a motive in the story, at some point you're going to have to use it to help develop or resolve your motives. Strive to make all of the elements in your compositions irreplaceable and you might be lucky enough to be able to create works that become irreplaceable.