Henry Jekyll's fault was a dual one. He had, on the one hand, a desire for gaiety, but, on the other hand, a keen fondness for the respect of fellow professionals to the extent that he assumed a more studious and severe countenance in public. These two dichotomous and irreconcilable sides of him fought with each other and he felt a morbid shame.
The thing that was difficult about this fault was that he was never a sincere, genuine individual with personal integrity in his personality or his life choices. When he gave in to his lower impulses, he was no more fully himself than when he assumed a seriousness that was beyond his sincere degree of earnestness and studiousness. This continual posturing for relief on the one hand and for impressiveness on the other, was a continual strain that degraded his inner character.
At first, Dr. Jekyll did nothing about his faults except to give into them. And when he finally and ultimately gave in and sampled his dangerous experiment, he was gradually turned from respected professional to horrific monster with no civility, no decency or restraint or goodness at all.
basically what she said