Most bloggers and webmasters are so obsessed with optimizing their blogs / sites that they forget the most import thing of all. A site must have quality content to get visitors to return again and again.
SEO is important to getting indexed in the search engines and to bring organic search engine traffic but basic SEO should only take a small amount of a bloggers time.
People spend hours trying to get back links when only a few reciprocal links to your blog are necessary to be found by Google.
You have seen this written more than once Write for People Not for the Search Engines. Writing for people means writing high quality content. Quality content is automatically search engine friendly as it will be filled with keywords that people use to search the internet.
You can have a large amount of web traffic but without solid content visitors will not return.
Here are links to some past articles to help with the above:
Write Articles People Want to Read