In this passage, the narrator expresses profound shame and regret over his past actions, recognizing that he behaved in a way that was cruel and unworthy of his perceived character. He is surprised by his own cowardice, especially considering his belief that he was a good person.
The quote reflects a moment of self-awareness and remorse, highlighting the contrast between his self-image and his actual behavior, which he now laments as shameful and cowardly towards a friend. It underscores themes of guilt and the capacity for self-criticism in difficult situations.