He never made the mistake again. In American English, single quotes are never the default. They only appear inside double quotes. So remember: double quotes for the main quote, single quotes for the “living single” inner quote.

From that day on, Sam imagined a font called . Every time he reached for quotation marks, he asked: Is this quote living alone inside another quote? If yes, he used the “Living Single Font” (single quotes). If not, he used double.