Absorb What Is Useful

"Absorb what is useful, discard what is useless, and add what is uniquely your own." - Bruce Lee

Maybe I'm partial to Bruce Lee since the very first art I studied was Jeet Kune Do, but biased or not it's good advice.  However most people, if they do apply this concept, only apply it directly toward the technique aspect of their martial arts, and even then they seem to tend to restrict it to martial arts.  Let me give an example, an artist finds that a particular elbow strike from his art is ineffective in a certain situation, he learns about a differing method for executing a similar strike in another art that would be far more effective so he learns it and implements it.  That's the standard example.