Some consensus
One main reason that countries plunge into prolonged periods of decline is the absence of consensus. Greece has paid dearly for this. With a little consensus, we could have had private universities, we could have avoided bankruptcy and could have exited the bailouts much earlier. And the country would have been in a much better place in 2015 if we had elected a president on time the previous year and avoided elections.
But we do not learn from our mistakes. The current prime minister speaks of consensus but promotes division. The government sets the tone and the opposition follows. This vicious cycle must be broken if we do not want a repeat of the bankruptcies and national crises.