Failure is a big part of life.  In fact, I'm sure if we kept a record of how many new things we tried and how many we failed at, we would find that, except for when we were babies learning the basics, we fail far more often than we succeed.  Positive thinking gurus tell us we can succeed at anything within reason if we believe we can, so why do we fail so often?
    Part of it is right in that last sentence: we don't believe we can.  We may say that we want to climb mount Everest or write a novel or run a marathon, but if we don't really believe we can do it, we will fail.  Sometimes, we consciously believe we can do something, but our subconscious is telling us we can't and, when such conflicts occur, the subconscious always wins.  Another reason is that sometimes failure is good for us!  We would get spoiled rotten if we succeeded at everything we tried.  Plus, we may fail at one thing so we will move on and try something else that we are destined to succeed at.   
     When it comes to matters of spirit and our goal of spiritual enlightenment, most people fail because we feel we are not worthy.  That for some reason, we are not suited to be one of God's Chosen.  This is a very common feeling but we have to remind ourselves that it simply isn't true.  That simple fact that you were led by the unseen Forces of Light to investigate and become involved in spiritual growth is proof that you are worthy and it is a path you should pursue.