St. Teresa said  
  -  that "your good works and your prayers  
             should have a sure foundation.
             (This is especially important 
               if one is receiving many spiritual consolations  from God)
  -  "that the first stone of this foundation 
              must be a good conscience and 
      She emphasized the necessity
             of having a well-formed conscience 
       in order that:
        -- one can recognize what is sin or a fault or neither.   
        -- one can then  "make every effort to 
                   free yourselves from even venial sins and
                   follow the greatest possible perfection"
  As a result of  error and also laxity 
         which we observe in the world around us, 
  subtlely and gradually, our own judgement can be affected.    
  Then, our own imperfectly formed consciences 
         can give us bad counsel.
So, as St. Teresa says, 
    it is important to 
        avail ourselves frequently 
             of the sacrament of Penance and also 
        seek counsel and guidance from our Priests 
        who have "learning, spirituality, and experience" since:
 "Everything depends on our having true light 
         to keep the law of God perfectly. 
   This is a firm basis for prayer"
