There's no doubt that we're in a tough market. Even with the Aug. 23 follow-through day, conditions are rocky due to worries about the global economy. While many breakouts have occurred, albeit some from short bases, big winners have been few. Some are struggling or have returned gains. In these tough times, following the rules is crucial. Sell any stock that falls 8% below your purchase price. Arco Dorados (ARCO) is one rare winner. The April IPO