Is it a condition of filial piety not to feel disgust or negative emotions when doing what they ask?

This feeling (of distress and revulsion towards the father) carries no sin, as it is not by one's choice. However, one must not show any of it to the father, and should strive to honor him and treat him well as much as possible. For the heartfelt emotions that a servant does not choose, he is not held accountable.