Complex sentence: It is debasing and embittering to attack secretly those whom one is forced to praise in public; hence Berlin became personal in his polemics, and nervous and dissatisfied with himself and the world, because he knew himself to be misunderstood through his own fault.
Split into simpler sentences: It is debasing and embittering to attack secretly those whom one is forced to praise in public. Hence Berlin became personal in his polemics, and nervous and dissatisfied with himself and the world because he knew he was misunderstood through his own fault.