why does the mariner say that 'no sweet bird did follow'?

When the mariner had killed the albatross  he was very sure of his deed. However, he was filled with guilt of his crime and wanted redemption from the sin of killing the bird. When the weather worsened, he was sure that the bird could have solved the problem and cleared the weather. This is when the albatross seemed 'sweet' and was being missed. That is why the poet says 'no sweet bird did follow'. 

Hope the reference is clear. Happy to help!