No, I'm not talking about your spouse. I'm talking about those of us that get "married" to one training principle. We can get fixated on an idea, a method. Our fixation can shut out information provided by other methods that we've ignored.
Lots of coaches, trainers, and athletes have the best training method. If you specialize, then great. Continue to refine and specialize for your sport, but don't be blind to the benefits of other styles. For the rest of us (and I'm looking at you, crossfitters), expose yourself to every type of training possible. A good crossfit regimen SHOULD include just about every useful strength and conditioning style: weightlifting, calisthenics, strongman, powerlifting, speed-work, etc. Our sport requires you to be well-rounded and what better way to be complete than to try everything. Most of all, it keeps things fun.
Simply put, closed-mindedness is a recipe for halted learning. Try new things, play new sports, have some fun.