There is so much pressure on you, as a parent, to be perfect. You've seen the judgmental look of a passerby as you wrangle your child into the car. You know the guilt that comes after reacting in anger to your child's innocent (but annoying) plea for attention. 

As a child, you tell yourself the story that preserves your sense of safety: my parents are good and have it all under control. Safety is a primitive, inherent need you have and your growth as a child depends on it. You're completely dependent on your parents and if they weren't good enough and couldn't provide this sense of safety, the fear would capsize your child self and stunt your emotional and interpersonal development.