I was attending a lecture by a neuropsychologist once (I wasn't really, this is a joke, and I know it hasn't started particularly promisingly, but bear with me), the purpose of which was to tease out any causal relationship as may exist between frequency of intercourse and happiness. The speaker began by asking for a show of hands by those who had sex three times a week or more. A number of the audience raised their hands, and it was noted that outwardly, they appeared a cheerful, happy lot.
The speaker repeated the question, with reducing frequency each time, and sure enough, those who had the least sex appeared to be the most morose. To illustrate the point, she asked if anybody would be brave enough to volunteer whether they had sex, on average, perhaps once a year. At that point, a middle aged guy at the back of the room stood up, waved his arms about and with a maniacal grin on his face loudly proclaimed 'Me! Me! I do! Me!'
Now, at this point the neuropsych was clearly nonplussed. Addressing the inexplicably enthusiastic virtual monk, she asked why he appeared so delighted to be having sex so sporadically that most others would regard it as a tragedy.
'Because', enthused the man, 'It's tonight!'