How do you stop being grumpy?

I got into a grump today over something that I suspect has happened, which will royally piss me off if it has, but which I have no confirmation of yet.

I'd love to have the personality of someone who can wait and see if the bad thing has actually happened before flipping out, but no. I'm angry now about a currently hypothetical problem. Most likely it will stay hypothetical.

What do you do to talk yourself out of a bad mood? I've already tried going for a stupid walk, petting my stupid cat, eating my stupid favourite food, etc.