You want your website to be a hub of knowledge on its topic, a leader in its field, an authority-filled virtual gathering place for your audience. After narrowing down your keywords to a select few that you want your site to rank for, you create content that uses them. And uses them. And uses them. Eventually, you get into keyword cannibalization territory, and that content you’ve written becomes harmful to your site, rather than helpful.
It feels counterintuitive, but the more you try to optimize for the same keyword(s), the worse your website is going to perform. Making your own site compete against itself for the top spot in SERPs spreads ranking too thin, and what could have become a top 10 or even a #1 search engine result gets pushed down.
That’s what happens with keyword cannibalization. Two pages on your site are so similar that neither one gets a full investment from search engines. It’s impossible to know the full potential of one if the other is stealing some of its glory.