Former Fed Chairman Alan Greenspan warned of the dangers of complacency and excess when he had a rare moment of humility. In 2005, as his term as Federal Reserve chairman came to an end, he told Congress that those experiencing long periods of stability are more likely to overstep their limits.
Source: https://www.bloomberg.com/opinion/articles/2026-06-26/greenspan-deflated-one-bubble-his-own-authority