Stating the obvious as another sign of impending doom
More signs that your company is turning into corporate hell: someone sends out a notice stating that everyone should look out for their own sanity and enforce rules regarding meetings. Those meetings are to be cancelled, ignored, or aborted by walking out if they are pointless.
If you have to be told that, you're in trouble.
The higher up the source, the worse that trouble is. If your boss tells you these things and you're some leaf node on the org chart, that's one thing. If it's your CEO, well... it's something much bigger.
The next memo will be along the lines of "inhale, exhale, repeat".