Recently I have begun to research SEO in a much more detailed and comprehensive way. SEO is like those piano exercises from Czerny; not music, but necessary techniques to play music.
So it is necessary to develop libraries of key words to include in your online writing; but at the same time not focus on those keywords. It is necessary to cultivate links, but not spam them. It is the difference between planting a garden and rolling out astroturf.
Matt McGee's piece in Search Engine Land, Ex-Googler: “To Please Google With Your SEO, Forget About SEO” indicates that this is the correct way to think about SEO. You can't forget SEO, no more than you can forget technique when playing music, but you can't let SEO guide your online communications. It is necessary to write for people, not software bots.