Navel-gazing: excessive focus on oneself (http://en.wiktionary.org/wiki/navel-gazing). Excessive is excessive, by whatever criterion. If you publish a text, or sing it publicly, you implicitly claim to have something to say that is of interest to others; Shakespeare etc. definitely had.

Naval gazing at the ocean horizon can drive you crazy as well.

Good lyrics can be about any topic, and so can bad ones.