LIBRA (Sept. 23-Oct. 22): In 1928, biologist Alexander Fleming launched a medical revolution, developing the world’s first antibiotic: penicillin. The drug made it possible to cure a host of maladies caused by hostile bacteria. His discovery was a lucky fluke that happened because his laboratory was a mess when he went on vacation. While he was gone, a bacteria culture he’d been working with was contaminated by a mold that turned out to be penicillin. You achieve a more modest but quite happy accident soon, but it may depend on you letting things be more untidy than usual, though.