She always thought that she was very bad, with no face, no figure, no knowledge, no good family background, no man would want her even if she was cheating, so she might as well not care about anything, indulge herself, and have fun...
He didn't understand, she was obviously very cute, why did she always talk about how bad she was and didn't cherish herself so much? Was this an excuse for her own indulgence? He must educate her well!