"A master is one who has methodically changed the personality so that the personality is a window that is clean of debris.  The way you do that willfully, as students of the Great Work, is that you prepare your vessel for a new wine.  The vessel is the mind and the body.  You prepare it for a new wine.  The wine is the Holy Spirit." ~Ramtha 

    There are, of course, many types of masters, but we are concerned only with the spiritual adepts, also called masters.  The goal for each of us in studying spiritual enlightenment  is to achieve this: to become a master adept and teacher so that we can help our brothers and sisters as well as ourselves and, most important of all, help God's great plan.  As this quote from Ramtha indicates, this is a difficult and time consuming process.  Remember that the Holy Spirit didn't descend upon Jesus until he was an adult and had been baptized by John the Baptist.  That event was considered important by the early disciples and that day called Epiphany was one of the most important holidays in the first few centuries of the Christian Church.  
    But what does it mean to become "clean of debris" and "prepare your vessel for a new wine"?  It means that we have to change ourselves to become worthy of having the Holy Spirit within us and the Wisdom of the Ages revealed to us.  We have to get rid of our negativity, both in terms of negative thinking and negative, or very weak, energy in our energy centers (chakras).  We have to rid ourselves of very materialistic thinking.  There is nothing wrong with wanting a new car if your old one is falling apart, there is if you already have five cars.  It means we have to think of others as much, if not more, than we think of ourselves and our own needs and desires.  
    So how do we make all those changes in ourselves?  We do it one step at a time, do as much as we can, and ask God for help, because we can't do it without Him.