"This man who is a true Christian is at his highest when he feels the lowest and he is lowest when he feels the highest.  
He is in the least danger when he is fearful and trusting God, and in most danger when he feels the most self-confident.
He is most sinless when he feels the most sinful and he is the most sinful when he feels the most sinless."
 
[A. W. Tozer, "Tozer speaks"]