Code should always by itself document the "how" of the code, otherwise the code most likely isn't good enough. Something the code can never do is explain the "why" of the code, something that a lot of programmers skip. If you ever find yourself explaining the "how" in the comments, maybe run through the code once more and see if something can be simplified or variables can get more descriptive names.

For me, that's what was originally meant with self-documenting code. A shame lazy programmers hijacked the term in order to avoid writing any documentation.