One of the things that can slow-bleed the traffic from your site is the quality (or lack thereof) of the content you publish on your site. Previous Google updates like Panda have already been released specifically to deal with the issue of low-quality content on websites. Long story short: Panda intended to stop sites with bad content from appearing in the search results.
Keywords may get eyes on your content, but they won’t hold a viewer’s interest. You need something that’s going to keep them engaged, and keyword stuffing won’t achieve that. This is where the quality of your content is essential. Well-written, well-researched content keeps people reading, as it provides the solution they need, even if that solution is just something funny to fill a spare five minutes. It’s possible to enhance the content in many ways, such as formatting to arrange material in easily digestible sections, using infographics that are visually appealing and easy to share across social media, or creating videos that express ideas instantly. And don’t forget links. Creating a network of related content keeps viewers engaged with a constant stream of relevant information, and increases the chance they make a purchase.
Using the insight from the Data Cube can serve your blog content creation process in two ways. To begin, you will be able to create posts that align themselves well with what people seek online. This will increase the traffic to your page and help you to boost engagement. Secondly, since you are maintaining a steady stream of high-value posts that are tailored to the interests of your target audience, you will have a far easier time building consistent readership and encouraging people to move through the sales funnel.

SEO (search engine optimization) for organic search: SEO is a free method of SEM that uses a variety of techniques to help search engines understand what your website and webpages are about so they can deliver them to web searchers. These techniques include things like using titles, keywords and descriptions in a website and webpage's meta tags, providing relevant content on the topic, using various heading tags (i.e.

), and linking to and from quality online resources. 

Optimization techniques are highly tuned to the dominant search engines in the target market. The search engines' market shares vary from market to market, as does competition. In 2003, Danny Sullivan stated that Google represented about 75% of all searches.[63] In markets outside the United States, Google's share is often larger, and Google remains the dominant search engine worldwide as of 2007.[64] As of 2006, Google had an 85–90% market share in Germany.[65] While there were hundreds of SEO firms in the US at that time, there were only about five in Germany.[65] As of June 2008, the marketshare of Google in the UK was close to 90% according to Hitwise.[66] That market share is achieved in a number of countries.

Well, yes and no. Sure, you can get hit with an algorithm change or penalty that destroys all your traffic. However, if you have good people who know what they are doing, this is not likely to happen, and if it does, it is easy (in most cases) to get your visits back. Panda and Penguin are another story, but if you get hit by those it is typically not accidental.