I am something of eclectic reader.  If you look upon my book shelf, you will see books you may expect to find, such as Mixed Martial Arts by BJ Penn and The Art of War by Sun Tzu.  But, you will also find Good Omens by Neil Gaiman/Terry Pratchett, The Prince by Niccolo Machiavelli, The Ascent of Science by Brian Silver and The five people you meet in heaven by Mitch Albom.  I love to read and I am quite happy to read up on just about any subject.  I enjoy the fact that you are never quite the same once you have been touched by the messages conveyed by the author.  They change your perception, sometimes for the better, sometimes for the worse, sometimes rightly and sometimes wrongly.  It is quite the power that authors have.  If you connect with them, they can change how you perceive your world without ever having met you.  
Perception is a very wide encompassing word.  Within Martial Arts, I think it in relating to many areas.  It is how you view and interact with your instructor and your fellow martial artists.  It is how you learn the art form that is being taught to you via sight and touch.  It is how you grow in skill by recognising movements and developing timing.  We are aware of this, it is for all intents and purposes pretty common sense stuff.  
However, the real power with perception (as the authors of the above books now realise) comes from the individuals innate ability to change their own life.  Think about the feelings you have had in the past when you have felt good about life or inspired to do something.  Remember how buoyant you were and how you approached every other aspect of your life for that time afterwards in a positive way?  Why can we not feel that way more often?  Or can we?  Your life is pretty much made up of how you perceive it.  We are all capable of being so much more.  But, to create the life that we want, we must first change the way we perceive it.  I am as guilty of struggling with this as anyone else.  I have my ups and my downs.  That though is where martial arts comes to fruition within my own life.  The self discipline instilled in me through regular training is what I try to draw upon constantly to pause, reset and change my perception of the world so that once again, I find myself back on track.  The study of martial arts is essentially about bettering yourself, but it is not just about the mastering of physical skills.  The real skill comes in the mastery of ones own mind and perception.  Through this, we not only change our own life, but also affect positively all the lives that ours comes into contact with.  So, now you know the answer to the question, "what do you, BJ Penn, Terry Pratchett and Niccolo Machiavelli all have in common"?.  You all have the ability to change your world....