why was Edger so convinced his bank would never close?

Edgar thinks that his bank had survived every conceivable catastrophe so it will never close,

"A monolithic structure of Indiana limestone built by his father in 1920, the bank stood like a gray fortress at the corner of Yulee and St. Johns. First National had weathered the collapse of the 1926 land boom, had been unshaken by the market crash of 'twenty-nine and the depression that followed. "The only person who ever succeeded in closing First National," Edgar often boasted, "was Franklin D. Roosevelt, in 'thirty-three, and he had to shut down every other bank in the country to do it. It'll never happen again, because we'll never have another s.o.b. like him."