One of the ways you'll grow your income is by focusing on the 20% of copywriting work that produces 80% of your revenue. I mention this because I'm a big fan of the 80/20 principle, which basically says that 20% of effort produces 80% of results in any situation. The precise percentages sometimes change, but the principle itself holds true.
The difficult thing is to actually practice the 80/20 principle. For instance, one of my clients offered me a significant amount of work yesterday, but he wanted me to do it for a very reduced rate. Applying the 80/20 principle, I had to say no. Of course, I hate to turn down work, not because I need it, but because of the intrinsic human behavior that tries to accomplish "more with more."
Instead, we must focus on "less is more" and "more with less." This is the only way we can ever gain full control over our time and income.
If you are interested in learning more about the 80/20 principle and how to apply it to your life, I highly suggest all of Richard Koch's books on the subject: The 80/20 Principle, The 80/20 Individual, and Living the 80/20 Way.