When you are content writing for you site, you do need to keep in mind the user freindliness of your website. I read this great article about usability that gave an analogy of a restaurant that did tons of advertising but didn’t reap the benefits because their restaurant wasn’t quality.
Write the content for your website in a way that is going to satisfy the people who read it. Filling pages with empty words that happen to match with your keywords will be much less successful than useful information that is relevant to your clients needs.
Don’t focus on your rankings because you will become obsessed, checking other peoples sites and wondering why they are ranking higher. Take that energy and devote it to writing relevant website content! When you have quality information that converts visitors it is far more valuable than just sheer numbers.