Germany used to be at the heart of European integration. Its statesmen used to assert that Germany had no independent foreign policy, only a European policy. After the fall of the Berlin Wall, its leaders realised that German reunification was possible only in the context of a united Europe, and they were willing to make some sacrifices to secure European acceptance. Germans would contribute a little more and take a little less than others, thereby facilitating agreement.
Those days are over. The euro is in crisis, and Germany is the main protagonist. Germans don't feel so rich any more, so they don't want to continue serving as the deep pocket for the rest of Europe. This change in attitude is understandable, but it has brought the European integration process to a halt.
By design, the euro was an incomplete currency at its launch. The Maastricht treaty established a monetary union without a political union – a central bank, but no central treasury. When it came to sovereign credit, eurozone members were on their own.