"I cannot do this anymore" reflects a deep sense of emotional exhaustion and helplessness. The speaker feels overwhelmed by their ongoing struggles and doubts their ability to recover or continue fighting against their inner pain. The exhaustion seems to have reached a point where resilience feels impossible, emphasizing a moment of personal crisis.

"I cannot pull myself together again and spend the next fifteen hours of wakefulness" highlights a feeling of being trapped in a cycle of anguish, where even trying to stay alert becomes futile. The statement underscores the overwhelming nature of the speaker's misery and their sense of losing control over their emotional state.