More additions to my ongoing Unfinished Manifesto:
Don't be afraid to fire clients. If you've never fired a client, you're probably compromising your values at some point. Obviously, it's tough to fire clients, even bad ones. It's only human nature to look at the money you make from some clients and rationalize reasons for keeping them. But if you really are your own boss, then you work for YOU, not them. This may sound harsh, but it's true.
Occasionally surprise your clients, even after they get used to it. I call it the Expected Surprise. It's what you have when you open a box of Cracker Jacks or when you go to Disneyland for the 43rd time. You know you're going to be surprised, you just don't know what the surprise will be. Create that same situation with your customers.
Maintain healthy paranoia. I actually learned this first from Phil Wexler. We were having dinner about 18 years ago, early in my speaking and consulting career. I asked what it was like to be a million-dollar a year generator. His response was, "I'm deathly afraid the phone won't ring tomorrow. I've got to stay paranoid."