According to Thoreau, how does his willingness to break the law improve government?

According to Thoreau, breaking unjust laws forces the government to rethink and change those laws.....

If the injustice has a spring, or a pulley, or a rope, or a crank, exclusively for itself, then perhaps you may consider whether the remedy will not be worse than the evil; but if it is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law. Let your life be a counter-friction to stop the machine.