Quoting again from The Introvert Advantage by Marti Olsen Laney, PsD., this time her sidebar in the Chapter on Personal Pacing. This is a list of symptoms indicating the Introvert has overloaded, drained away all her energy and is in sore need of rest and solitude to re-invigorate:

Anxious
Agitated
Irritable
Trouble sleeping
Unable to think (recall things)
Unable to concentrate
Unable to make decisions
Confused and Discombobulated (as if dashing from thing to thing in a blur)
Drained, tired, put upon, pooped
Disconnected from self

In recent weeks I’ve suffered from all of this. At the same time. I have introverted and semi-introverted friends who have as well. You begin to wonder what is wrong with you. Am I going crazy? Now, though, when I see this array of symptoms appearing in my life I know it’s time to hold the line and retreat to the Fortress of Solitude for a time and just rest.

Amazing what just a little bit of that does.