Thank goodness that doesn't happen often but when I have had enough I declare some time away and let calls go to voicemail and let emails get the auto response. Nothing is so important that it can't wait a few hours.

Oh yes.  too often, too.  I try to take a hot bath and go to bed early and hope it's better the next day w/ more sleep.

I meditate and exercise regularly which helps me stay balanced even when things/people get crazy. Humor also helps!

I drive.  I just have to leave my office to run an errand and get away for a while then go back and get back at it.

Yes I do Mark, that is when I ask for some help from family and staff while I take a few hours off.

Eventually getting back on the phone ends all of these lulls.