Her attitude did more than make her sick. It ended up alienating her from the ones who could help her the most. The nurses flipped coins to see who would be stuck with her. The downward spiral. Anger, resentment and self-pity set us up for failure.
Psychologists call it a downward spiral.
By dwelling on negative thoughts, you start to feel crummy, then you act crummy, which makes people treat you crummy, so now you have a valid reason to be negative, and you feel even crummier. Jesus says the downward spiral also applies to spirituality. He says the first corrupting thing out of the heart is evil thoughts. All other sins follow from it. The thoughts take concrete form as sins.