I do that too. I used to get into trouble from my teachers from singing out loud in early elementary. I did it because I had to drown out all of the noise before it drove me crazy or made me go catatonic! But the only time I've banged my head is during the worst of hard labor. I figured the pain in my head would be preferable to the pain of labor; until the midwives threatened to restrain me.
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"Honey, would you buy me some boobles for my 40th b-day?" "No way, they're too expensive. Your own baubles will have to do."