It makes sense that an octopus squeezing the crap out of one's brain causes pain. The victim of the angry octopus then clutches his or her head, and exclaims something similar to the phrase, "AAAGH my head bleep bleepity bleep OOOW!"
The pain of angry octopus headaches causes people to think garbled thoughts and react strangely to common situations.
Angry octopus headaches can also cause delusions.
The only thing that frightens away angry octopuses is coffee. They don't like coffee at all.
Unfortunately, this enmity between coffee and angry octopuses has two downsides:
1) Coffee is what makes angry octopuses angry. Scaring away an angry octopus with coffee only makes it angrier, and then it returns to squeeze one's head even more viciously.
2) Drinking coffee to rid oneself of an angry octopus headache in the evening is not an option if one desires to sleep that night.
If you ever find your brain in the grip of an angry octopus, fret not!
Actually, you may fret. You are now part of a vicious cycle where you must choose only one: proper sleep, or painlessness.