A lot of people screw themselves up when they're building internal links because they link irrelevant content to their target keyword.
If you have a target keyword that you're trying to rank for, make sure to create content that actually delivers on the search intent behind that keyword.
Otherwise, you're just wasting your time.
It's only a matter of time until Google catches wind of what you're doing and penalizes you or ignores the link.
Follow this rule of thumb: Make sure that whatever keywords you're targeting are actually delivered by the content of the page.
Next, make sure that the content of the page you are linking to is enhanced by the page you are linking from.
If you follow these rules, you're putting your customer front and center, and Google is more likely to reward you.