It's been a while since I've done one of these posts, so I figured now would be a good time. Again, these aren't meant to be law; they're just pieces of advice I've learned along the way that I think would be helpful to people who are thinking about (or are currently) writing a book.
I remember a quote from one of the members of Hot Water Music: "We write about what pisses us off." Now, Hot Water has always done a great job of conveying anger without sounding immature or lackadaisical. So I would not recommend saying something too broad and hurtful like, "You suck." That said, and where I'm going with this, use the anger you feel about something and let that motivate you to write something.
This is definitely the kind of stuff Stephen King so eloquently put in On Writing: let your life dictate your writing, not the other way around.
While I was writing POST, a lot of stuff motivated me to get things done. Just merely seeing a copy of Nothing Feels Good on my book shelf was plenty. But I was also frustrated with where my life was going up until I started writing the book, and I wanted to do something more with my life than just going to and from work and listening to music and watching DVDs. That's plenty there.
Without going into specifics, there are some things going on in my life now that are really helping me stay on track with When We Were the Kids. Anger I have about certain things are keeping me motivated with fleshing out these many characters I've come up with, and the scene they were a part of. Just writing this stuff out is a really great way of dealing.
There's a common adage that great work comes from depression, loneliness, and sadness. In other words, great art comes from great suffering. Well, that can be true, but I think it's important that you understand that stuff rather actually live that stuff everyday. If you lived that stuff every day, you might not live very long. Just a reminder: Bukowski didn't live every minute of every day of his life drunk and alone.