Writing is a lot like smoking weed. If you smoke the same strain all the time, you don’t get any higher by smoking more. You just get lower on weed.
Writing is the same, in that one has to have more than one voice. This is despite the fact that it is generally considered that “multiple voices” are sure sign of mental illness. One of these statements is true. Or both. I’m not certain that the two ideas are mutually exclusive.