Self-talk occurs more during golf tournaments than daily life. Self-talk is frequent but not constant in competition. Inner-speaking self-talk is 6 times as common as aloud self-talk. Effortful deliberate System 2 self-talk is rare. DES avoids distortions from retrospectives and questionnaires. Golfers trained as DES participants in natural settings. DES works in live sport environments. Self-talk boosts athletic performance. DES captures ongoing inner experiences accurately.