From Self-Esteem, page 17:
"The critic has many weapons. Among the most effective are the values and rules of living you grew up with. the critic has a way of turning your"shoulds" against you. He compares the way you are with the way you ought to be and judges you inadequate or wrong. he calls you stupid if the A you should have had slips to a B. He says, "A real man supports his family," and calls you a loser when you're laid off from work. He says, "The kids come first," and calls you selfish when you crave some nights off."
In addressing many neurotic mental health issues, you'll come across the concept of rigid thinking, and how it contributes to depression, anxiety, etc. The paragraph above demonstrates how this type of thinking leads to misinterpretations of environmental activities, which then leads to negative/maladaptive feelings, which in turn lead to less optimal behavioral responses. Albert Ellis is generally credited with the modern therapeutic framework for addressing rigid thinking patterns and their unhealthy impact on our well-being (Rational-Emotive-Behavior Therapy, or REBT).
When tackling low self-esteem, adressing rigid thinking patterns (as voiced by this "inner critic") is of paramount importance. The book goes into some detail as to why, as well as how to confront these cognitive errors. For now, let us just say that, in general, excessively rigid thinking is, first and foremost, wrong. Period. To consistently judge oneself against erroneous standards, then, puts us at a disadvantage. This is why confronting the inner critic, and correcting the rigid beliefs inherent in the inner critics' statements, is so important. Next up, I'll provide further quotes from the book, and provide a few examples.