He was conscious of being irritated by ridiculously small causes, which were half of his own creation. Why was he making any fuss about Mrs. Casaubon? And yet he felt as if something had happened to him with regard to her. There are characters which are continually creating collisions and nodes for themselves in dramas which nobody is prepared to act with them. Their susceptibilities will clash against objects that remain innocently quiet.
The narrator reflects on a character who feels inexplicably irritated by trivial matters, many of which they had a hand in creating themselves. One specific source of this irritation is Mrs. Casaubon, yet the character is aware that they are overreacting. This inner turmoil suggests a deeper conflict stemming from their perceptions and expectations.
This dynamic demonstrates how individuals can fabricate tensions and disturbances in their lives, often leading to an emotional response towards others who are unaware of the internal drama unfolding. The character's experiences highlight how personal susceptibilities can produce unnecessary friction with the outside world, creating interactions that feel charged even when the other party is indifferent.