SEO, an ongoing process.
One of the complaints I frequently see is the mournful cry of “But I haven’t changed anything on my site so why am I losing ranking?” This attitude, and the immediate assumption that a penalty, filter or algorithm change is at fault ignores a basic truth about the very nature of the web.
You aren’t the only one out there.
It seems obvious but it can be easily forgotten if your vision becomes too me-centric. You can become obsessed with beating the algorithm and forget that you aren’t the only one trying to do so. So then you get to the top and there is a tendency to think, “That’s it, I’ve made it.” But your competitors aren’t standing still, unconcerned that you outrank them. No, they want your ranking. And being number one just means you’ve got that many more competitors behind you who want you’re spot. It’s the rare company that wants to be number 5. As Will Rogers said, “Even if you’re on the right track, you’ll get run over if you just sit there.”
What does that mean to you? It means that you can never rest. SEO doesn’t end after a single round of edits and polishing. Continue to add good relevant themed content, continue to go after expert back links, monitor your competitors and keep an eye on their keywords and resources.