Have you ever had a gold fish bowl or an aquarium?  When you first put fish in them they occasionally bump into the glass.  After a while they learn how far they can swim without bumping the glass and will swim faster without problems.  Move them into a larger bowl or aquarium and for a while they will continue to swim in the same limited area.  Gradually, due mostly to mistakes, they will swim in a larger area until the now use the whole space again.

Chain a baby elephant to a stake and after a number of failed attempts to pull out the stake, the baby elephant will stop trying.  After the elephant is fully grown the same chain and stake will hold him even though he can now easily pull it out of the ground.

We all do the same thing in various ways.  We limit what we think we can do based on problems we had in the past, things we've seen happen to others, and things well-meaning people like our parents and teachers told us. 

A grade school art teacher's comment on your class project make you decide to quite drawing or painting even though you love doing it and might have developed the skills and talent given time.

A parent telling you to stop wasting time with your garage band makes you give up music.

A dog that bit you when you were three makes you fear dogs for the rest of your life.

A minister tells us we are sinners, evil, and not worthy to speak to God.

We all have programmed these types of limitations into our subconscious minds.  The successful person, whether it be in business, arts, or anything else learns to overcome irrational limitations.  The person seeking spiritual development must do so as well. 

It is especially important when seeking spiritual enlightenment, that you free yourself of limiting concepts of what God is, what the universe is, and what you are so those subconscious filters don't block you from the learning the truth.