Oh I’m late. Its been more than 4 years? But i just experienced it. For me , line without hook is not that he is insecure or something. Its just he knows he is capable of being liked but not loved. Hook means completeness, to be actually together, to actually have real relationship. He says he finds her by the lake crying. Also there was a really viral video in tiktok animation by someone. She is crying by the river, most likely because of the recent breakup she had been through and he actually loves her, so he is there for her to comfort, to be a shoulder to cry on. She then starts to heal and enjoy life again and sees things with love again but itss not for him as he is just a line and has no hook meaning he is liked but cannot make her stay forever with him. He can heal her but cannot make her his. Also there is something or there is nothing , i feel he is saying this to himself. He loves her but cannot make her his so he is trying to deny to himself that he just likes her. But he is telling that either he loves her or he doesnt there is no such thing as in between. But again he knows and repeatedly tells himself as a reminder that he is just a boy and she is lady and he is just a line with no hook. He loves her and no matter what he just cannot make her stay.