Does this affect the rankings of your page, or does it instead of work like an "adding" effect where more link juice is created as you internally link?
Tl;dr - You don't lose ranking. But you can if you don't do it right.
I would like to burst a bubble for you. Terms like "link juice" are basically SEO mumbo-jumbo made by SEO marketers who want to sell you a ccourse/product.
If you think pages have some mythical stuff called link juice which "flows" And in turn causes some drop in the page ranking because the "link juice has flown out", then nope, That doesn't happen. That's SEO mumbo-jumbo.
when you link a page 'y' on your website from page 'x' that is on your website too (I shall abbreviate this as page x->y) 2 things happen:
- you make page y "more crawlable". Googlebot (and other search engine crawlers) follows links recursively. that is, it follows each and every link that is on your page 'x' and adds it to a list of links which later get processed and get added to the googles index.
- You add an extra item in page Y's backlink count.
Now, Google (and other search engines) cares a lot about backlinks. So if your page X ranks at the top of serps and page X links to page Y, google thinks "it should be good" cause a high authority page is linking to it.
There's no loss of rankings or as you called it "an adding effect".
The same happens for external linking, the only difference is this time it's not your page that you help to rank.
However, You can lose rankings for page X when linking X->Y when you have too many internal links on X. Then google thinks you are linkspamming and gives you a penalty.
Googlebot also has a crawl budget so google may not crawl all pages that you link. So say if you have a 5000 word article and you link to 50 internal pages, google may only visit 25 of those.
