“The more you play baseball, the less depends on your athletic ability. It’s a mental war more than anything.” – Alex Rodriguez 
Now I can’t speak for A-Rod, but I would imagine he wasn’t condoning less physical training. Rather, he was emphasizing the importance of winning the mental battle that is always ensuing in our minds. As you increase in skill and move up the ladder of competition, you will soon begin to understand Alex’s point. Very little separates the collegiate starter and the bench warmer. Even less separates professional players from their counterparts that are still playing Triple-A. Most of these players can field excellently and hit the ball well. The difference? Whether or not they are winning the “mental war.”
Do all the secrets to becoming the mentally strongest ballplayer in the world lie below? One of them does! The strategy of pairing our desired feelings with an action has been known by psychologists since the late 1800’s! It’s only recently that we have taken these incredible findings and put them to work in the sport world. 

The Breakdown: Ivan Pavlov, a Russian physiologist, found that when he introduced meat to his dogs with the pairing of a chime, the dogs salivated. This was entirely due to the scent of the meat, and nothing to do with the sound of the chime; at first. After many trials of providing the meat, along with playing the chime, the dogs soon began associating their food with the sound of the chime. The breakthrough occurred when Pavlov played the chime with no meat in the room, and the dogs began salivating. They had been classically conditioned to associate the chime with their lunch!
Making this Relevant to You: We are no different than those dogs. If there is a feeling that you want to be able to exhibit on demand, pair it with a physical action. Do you want confidence on the fly? Great. Next time you’re feeling confident (listening to a great tune, watching an inspirational video, receiving you’re A+ grade), do a consistent physical action (snap your fingers, shake your head, slap your thigh). The keys with this strategy are repetition and consistency. Every time you are feeling your desired emotion, anchor it with the SAME physical act. After a while, you will have primed yourself to react to your physical anchor with your desired feeling. At the plate, in the bottom of the 9th? Step out of the box and snap your fingers. You might be surprised with how you feel.