Deviation From Expected
Someone sitting at a distance asks for the water bottle near me. I pick up the bottle and throw it at them. Surprisingly, the cap is not screwed. Water splashes all over. When a bottle has its cap on, we usually expect it to be screwed tight. When something deviates from the expected, unless there is an indication saying so, it creates trouble and confusion.
The same principle applies to systems and application design. For example, let us say that you have a development server where someone is running a production cron job. Since this is a development server, someone might take it down for experimentation. No one expects the non-availability of a development server to have untoward consequence.
Whenever you deviate from the expected, ensure you scream from the top of your voice so that it is not missed. Documentation, common conventions and putting in the right processes are some of the ways to mitigate this. The best is not to do it. Whatever you are doing, it always helps to ask, is this a deviation from the expected? If I am not part of the inner circle, would I expect it to be like this?