YOU can understand the self-congratulation. In the early hours of October 27th, after marathon talks, the leaders of the euro zone agreed on a “comprehensive package” to dispel the crisis that has been plaguing the euro zone for almost two years. They boosted a fund designed to shore up the euro zone’s troubled sovereign borrowers, drafted a plan to restore Europe’s banks, radically cut Greece’s burden of debt, and set out some ways to put the governance of the euro on a proper footing. After a summer overshadowed by the threat of financial collapse, they had shown the markets who was boss.