When the financial crisis hit Iceland seven years ago, Gudmundur Kristjansson, a 55-year-old fisherman with a wide smile, weathered face and mischievous eyes, almost lost his business. Interest payments on his loans soared 300 percent. He had to sell his two fish factories and two of his five fishing boats. “We didn’t invest for many years,” he said, “because we were only paying interest.”

His tribulations were shared by the whole country. After Iceland’s three largest banks fell in the space of three days, the currency collapsed, the stock market fell 95 percent and nearly every business on the island was bankrupt.

Short-term suffering followed, but today, Iceland is buzzing: Unemployment is 4 percent, the International Monetary Fund is predicting 4.1 percent G.D.P. growth for 2015, and tourism is booming. Mr. Kristjansson has just bought Nanoq, a used boat from Russia that recently was being prepared for a fishing trip to Greenland.

But just as Iceland returns to the fold, Europe is again bracing for a financial catastrophe in a renegade nation. Greece, having missed crucial debt payments, has in recent days moved closer than ever to an exit from the euro. Leaving the common currency — and having to suddenly create its own new money — could plunge Greece into an even deeper economic downturn.