On page optimization acts as a concrete foundation for overall SEO strategy apart from that it is totally focused on primary aspects such as indexation, crawlability and relevancy of the page. It is quite mandatory to optimize on page according to search engine guidelines without any compromise in website experience and usability.
Always make sure that the keywords that you are hoping for your webpage rank to must be present on the page otherwise it would be quite difficult to rank a website with irrelevancy factor. It takes quite a skill to determine which keywords is getting what amount of traffic, moreover how to rank a specific page on desired keyword.
The initial level goes like this:-
1. Finalizing keywords and phrases for targeting purposes.
2. Making sure website pages contains those finalized keywords naturally.
3. Molding specific elements of the webpage to assure presence of exact keywords.
Present age search engines are way much smarter than you could think of, they understand synonyms, singular and plural addressing to an exact same concept. For example “eating a chocolate” and “eat a chocolate” are the exact same things.
On page factors are very important, but they cannot rank a web page alone as other factors also a vital role, first and foremost delight the user and thereafter think about keywords & phrases. Your amendment of putting desired phrases into the content of the page must not affect the readability of the content as the user must be given way much preference than the SEO itself.