If you're writing an academic/research paper, you still have to find something to cite. "I know this stuff, just trust me" isn't a valid citation. The point is

If you're writing an academic/research paper, you still have to find something to cite. "I know this stuff, just trust me" isn't a valid citation. The point is to give anyone who reads the paper a way to a) verify that each fact you put in the paper has solid academic sourcing, and b) find more information about it if they wish. If you know a lot of stuff about the topic already, that's great—but unless you've already written and published papers on the subject, you can't just cite yourself.