Allow me to explain.
Of course you are a normal person with warts and flaws. But you have a person (s) in your life, through work, church, or some other limited environment with whom you have complete control of their "diet" of information when it comes to you. To put it another way, they only know you from what you 'feed' them. When you share a confidence about some conflict it somehow always comes out putting you in a favorable light.
For example: maybe you are having a feud with a third party and you tell your little rat how unfairly you are being treated and how long suffering you are. You keep your supporter up to date on all developments and soon they are ready to kill the other party for you! This sort of thing is common with marital problems.
Yes, of course it is human nature but is it good to cultivate a confidant that only hears your side? Is it really honest?
And, Have you ever had your cultivated lab rat come into contact with one of your unsuspecting villains?