I think this song is about Jimmy's own success. After his previous success, he expects "the jig to be up" and people will realize that maybe he isn't that talented -- his songs aren't original and his lyrics aren't good. His friends tell him his new music is good and he thinks they are lying -- his success will come crashing down once everyone realizes his music isn't that good and his success will just be a memory, like a dream.
I think this song is about Jimmy's own success. After his previous success, he expects "the jig to be up" and people will realize that maybe he isn't that talented -- his songs aren't original and his lyrics aren't good. His friends tell him his new music is good and he thinks they are lying -- his success will come crashing down once everyone realizes his music isn't that good and his success will just be a memory, like a dream.