I also have "Songwriters on Songwriting" and I find it very interesting that although there is a very common thread where many writers feel that they are simply a "channel" for the song, there are also many succesful writers who credit simple hard work and daily dedication.
Having written very many songs (but only a precious few "good" ones) I continuously try to understand the "muse".
The best (ie: most intellegent, profound) songs I've written were the result of a dedicated decision to sit down and write an intellegent profound song. However the majority of the songs I've written were the result of a "sudden" inspiration.
So after reading this book and applying it to my personal observations - it is clear that writing must be a combination of divine intervention, an elusive muse, a lot of hard work and a true love for the writing process.
I will have to find the "And Then I Wrote" book.