When it comes to SEO it is not always the case that more is better. You do need to ensure that you continually do Search Engine Optimisations and that should be made up of a mix of lots of different elements but be sure not to over optimise your site or a particular page.
If you have a page that you want to rank well for a certain search term, you may be tempted to put the phrase in your page as many times as you can. You may include it in the title, the heading tags, throughout the content and in the alt tags of any images. This can be seen to be spamming and you may find that not only does your page not rank any better it actually gets penalised and ranks worse than it did before.
You need to make sure that you get the balance just right. You may be able to use variations but be carefully as Google and the other search engines are clever enough to know that they mean the same thing. Instead, you may want to break your content down more in to useful sub headings. This will allow you to write unique content that is still very closely related to the main subject.