When adding content to your website, linking from one of your pages to another can be a great thing! As I’ve mentioned before (and a great example of an internal link), Google ranks individual pages, not full sites. Internal links help Google move around your site and get a better feel for the structure of everything.
Like most good things though, too much of that good thing can be a problem. Since Google uses those internal links to help understand the flow of your site, if every page on your site has hundreds of links to other pages on your site, it creates kind of a mess for Google to sort through and they can have a difficult time seeing the big picture.
As Google’s John Mueller recently said (via SEJ), when asked if too many internal links could be a problem:
I think, in the sense that we do use the internal links to better understand the structure of a page, and you can imagine the situation where if we’re trying to understand the structure of a website, with the different pages that are out there, if all pages are linked to all other pages on the website, where you essentially have like a complete internal linking across every single page, then there’s no real structure there.
I still encourage you to link liberally on your pages. If you can reference an old post or page that offers value to your reader, please link it! Your reader will appreciate it and Google will appreciate it.
However, if you think you’ve found a shortcut by putting dozens or hundreds of links on each page, you’re likely doing more harm than good.