A key thing I don't see mentioned yet is the importance of disengaging (or not engaging in the first place) with clients who are not a good fit for you. The problem is you often don't know at first what attributes to look for. It's very important to forecast what your business will look like in, say, five years, and then try to attract from the start only those clients that fit the model. Yes, this is hard if you really need income right now.

Sorry, I don't know any books or other resources regarding this topic.