The EU and the Maastricht Treaty were a joke from the start. Anyone with a wit of understanding Europe knew it. Yet they went ahead because this time it was going to be different. About that; If there is one common theme to the vast range of crises we consider, it is that excessive debt accumulation, whether it be by the government, banks, corporations, or consumers, often poses greater systemic risks than it seems during a boom. Infusions of cash can make a government look like it is providing greater growth to its economy than it really is. Private sector borrowing binges can inflate housing and stock prices far beyond their long-run sustainable levels, and make banks seem more stable and profitable than they really are. Such large-scale debt buildups pose risks because they make an economy vulnerable to crises of confidence, particularly when debt is short term and needs to be constantly refinanced. Debt-fueled booms all too often provide false affirmation of a government’s policies, a financial institution’s ability to make outsized profits, or a country’s standard of living. Most of these booms end badly. Of course, debt instruments are crucial to all economies, ancient and modern, but balancing the risk and opportunities of debt is always a challenge, a challenge policy makers, investors, and ordinary citizens must never forget. Yet the best and the brightest did because it was going to be different this time. Yeah.

Perhaps more than anything else, failure to recognize the precariousness and fickleness of confidence-especially in cases in which large short-term debts need to be rolled over continuously-is the key factor that gives rise to the this-time-is-different syndrome. Highly indebted governments, banks, or corporations can seem to be merrily rolling along for an extended period, when bang!-confidence collapses, lenders disappear, and a crisis hits.
Various sources.
This Time is Different is a book worth reading.