It all comes down to hard training; commitment and passion forged and molded by a great style and coach - and acute real-time awareness of your opponent's strengths and weaknesses. What's a great style? It brings all fight tools into play. Things like confidence, concentration/awareness, support, nutrition and rest sure can help too. There ain't no doubt about it: MuayThai is a great style with an amazing set of versatile tools and extremely dramatic history and legends.
Human fighting styles win acclaim with people - people who were ordinary once, but extraordinary events forged them into doing extraordinary things and legends are born. In the case of MuayThai, that person was Nai Khanom Dtom. (The sound of the "Dt" in Dtom is halfway between a "d" and "t.") In the 1765 Burmese-Siam War, the Burmese (from Myanmar) attacked the 417-year-old Ayutthaya Kingdom of Siam (Thailand), and sacked the capital. (That war was really a continuation of the earlier 1759–60 war.) After the sacking of Ayutthaya, many prisoners were taken to Burma. Among them were number of boxers including Nai Khanom Dtom. The Burmese King, Hsinbyushin, AKA Sirisūriyadhamma Mahadhammarāja Rājadhipati, AKA Mangra and 'Lord of the white elephant' organized a lavish series of religious festivals to celebrate his victory.
Among the entertainments was to be a highlight fight between one of the captured Siamese fighters and his champion Burmese boxer. Nai Khanom Dtom was selected among the Siamese fighters to be their champion. According to legend, he performed the Wai Khru ritual before the contest. As soon as the ceremonial gong started the match, Nai Khanom Tom launched such a furious barrage of kicks, punches, elbows and knees that he completely crushed his Burmese opponent. The referee however, to save face for the Burmese, declared the win invalid, claiming that their fighter was distracted by the "strange" Wai Khru which he declared a form of black magic. The Burmese king then asked Nai Khanom Dtom if he was willing to compete again to prove his skills and abilities. The Siamese champion said yes, and then went on to demolish nine Burmese champions one after the next. Quite astonished, the Burmese king then granted Nai Khanom Dtom his freedom, and some legends have it the other prisoners were released as well. Before departing, the Burmese king offered Nai Khanom Dtom a choice between two gifts. One was immeasurable wealth, and the other two wives. Nai Khanom Dtom was reported to have said wealth is easy to come by and chose the two wives.