Final answer:
The provided passages do not directly contain the quote where Ruthie thinks about persistent sadness, but similar themes of emotional struggle and depression are evident.
Step-by-step explanation:
The paragraph in which Ruthie thinks, "I keep willing myself to be happy, but there are days when the sadness arrives and sits on my head. It gets comfortable and stays there. Like a dark cloud that won't go away," is not directly provided in the passages given. This thought suggests an internal struggle with emotions and highlights a character's experience with persistent sadness or depression. The descriptions in the provided passages touch on themes of despair, struggle, and the psychological impacts of difficult circumstances, similar to what Ruthie appears to be going through with her own emotional state.