One of the best books that I recall reading in the past few years is 'In Pursuit of Excellence' by Terry Orlick. (I did a brief review of the book back in 2013). Some might call it a self-help book, but given the cheesy nature of that genre, I prefer to call it a sports psychology book - one that's applicable to all areas of life. In fact, it's published by Human Kinetics, a publisher of exercise physiology books, so it's not an altogether inaccurate description. In any case, exceptional performance has no real boundaries, especially when we consider the many psychological barriers that prevent us from achieving our goals and performing at our very best.
Throughout the book, Orlick drives home the importance of focus, not just your average type of focus, but absolutely immersing yourself in whatever it is that you want to do. In athletic terms, you might call it being in the zone - a point where absolutely nothing outside of that activity matters anymore. You essentially become one with whatever it is that you might be doing. Here's a quote that I think really drives home that point:
You can choose to be wherever you are—fully focused with every fiber of your being—or choose to be only partially there or not be there at all mentally.
Read that again, again and again: focused with every fiber of your being. People who have never been in that zone, may never understand what it means to get there, or how hard it is to maintain that level of focus, especially when assaulted by all of the modern day distractions that surround us, both internally and externally - our minds wander or some device nearby beeps or boops. This is the type of focus you will only ever draw out from within for tasks that you have a great affinity for, which is something Orlick also emphasises. There's no fooling yourself if the passion is absent.
You will slip up occasionally, no doubt about it, but simply reminding yourself to be there - absolutely in the moment, with every fibre of your being - somehow switches on a mental switch that takes your performance to a much higher plane. It works for me, and perhaps it might work for you. In fact, I have come to fully agree with Orlick when he emphasises the universal importance of focus:
Focus rules your life, your performance, my life, my performance. Focus rules the world because it directly affects every person, every experience, every performance, every family, every community, society, and the world—for better or worse.