Towards the end of January Busoni decided to abandon the projected visit to Paris. He did so with somewhat of a guilty conscience, and it is evident that he was beginning to suffer more and more acutely from overwrought nerves. He would never admit that he was seriously ill, and nothing would induce him to consult a doctor, still less to visit a dentist. [...] For years he had suffered from constant minor illnesses such as short attacks of influenza, but as far as possible he had disregarded them; over and over again he had fulfilled his contract to play, whatever his temperature might have been. Such things he regarded as all in the day's work of a travelling virtuoso. Gradually this neglect of health had told upon his constitution, and the anxieties of the years of war had naturally aggravated his condition. He was miserable if he was not working, but the only work which interested him seriously was composition. The older he grew, the more he detested having to play the pianoforte in order to earn a living; and it was the irony of fate that he should achieve his greatest successes as a pianist (to say nothing of the financial success and the more and more pressing need for that) at a time when he would only too willingly have retired completely, as Liszt had done, from the career of a public performer. [Dent, pp. 255-256]
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