Complex sentence: Instead of being habit, character is a "hexis" like health or knowledge, meaning it is a stable disposition which must be pursued and maintained with some effort; however, good habits are described as a precondition for good character.
Split into simpler sentences: Instead of being habit, character is a "hexis" like health or knowledge, meaning it is a stable disposition which must be pursued and maintained with some effort. However, good habits are described as a precondition for good character.