The "Beginner's Mind" or "Shoshin" is a concept in Zen Buddhism that refers to "having an attitude of openness, eagerness, and lack of preconceptions when studying a subject, even when studying at an advanced level, just as a beginner in that subject would."
Let me explain this in simple words. When you are a beginner in any activity, you focus all your energy and enthusiasm into accomplishing that activity. Your mind is devoid of unnecessary clutter and your concentration is solely on achieving the task at hand.
Remember the time when you were learning to ride a bicycle as a kid? While seated on the bike, were you not single-mindedly consumed with the process of conquering your dream vehicle... manouvering the handlebar, pushing the pedal, applying the brakes, et al? Your mind didn't wander even for a fraction of a second to think about what happened at school that morning or what mom was cooking for dinner. You were singularly aware and absorbed in the process of what you were doing at that particular moment. You were in your highest state of consciousness. You were operating at your peak performance levels!
In his bestseller "The Practicing Mind", Thomas M. Sterner calls this the "process-oriented, present minded state". He writes, "Video games offer a natural environment for pulling us into a state of focused present-moment awareness. If you watch people playing a computer game, you will observe how totally focused they are on what they are doing in that moment. Even though the best score possible is the ultimate goal, the participants are only superficially aware of it. The process of playing the game requires all their attention. If you talk to people playing a computer game, they may not even answer you because they are absorbed in the process of the game."
This is exactly how one needs to approach every task. One needs to be in the present moment and focus all attention exclusively on the process... while keeping the mind uncluttered and free of all pressures pertaining to the end result.
To achieve optimum results consistently, one needs to keep a "Beginner's Mind".