Complex sentence: The more depressed he got, the more difficult he was to work with, and this all worked against him because, for the first time in his professional career, Hackenschmidt faced a foe fully capable of defeating him.
Split into simpler sentences: The more depressed he got, the more difficult he was to work with. This all worked against him because, for the first time in his professional career, Hackenschmidt faced a foe fully capable of defeating him.