We're told we can get this disease and we believe it and vow to protect ourselves, and intend (really, truly) to stick by this rule, until we don't because we just can't, because it's just not fair, because our sense of entitlement exceeds our sense of vulnerability. So we blow off precaution again and again, and then we get scared and get tested, and when it comes out O.K., we run out of the clinic, pamphlets in hand, eyes cast upward, promising ourselves we'll never be stupid again. But of course we are stupid, again and again. And the testing is always for the same reasons and with the same results, and soon it becomes more like fibbing about S.A.T. scores 10 years after the fact than lying about whether we practice unsafe sex, a lie that sounds like such a breach of contract with ourselves that we might as well be talking about putting a loaded gun under our pillow every night.
That whole paragraph really conveyed to me the author's paranoia, which the author creates by having long sentences, listing scenarios, and repeating the word "again".