How do you know in advance that something that is nothing to you is a big deal to someone else? Is it wisest to always walk on eggshells just in case someone is a potentital loose cannon?

Some folks get wildly upset over very little. One wonders if something huge  and enormous and gigantic were to show up how they would react to that?  Do you flip out over nothing?  What would it take to cause you to flip and why?