According to the monster in frankenstein, why is felix so unhappy?

The monster man by Victor Frankenstein which is Felix felt unhappy of his situation because not only was he judged by his outer physical appearance but by also the suffering Victor set into him. Even if he killed Victor's best friend and its wife, Felix was not wholesomely evil. He even saved a drowning child and assisted the poor peasants, but was rewarded by disgust and beatings. He was sad of his current state, being a monster and being treated as one.