Gibbon's account of Diocletian in retirement is a classic (Decline & Fall of the Roman Empire XIII):
Diocletian, who, from a servile origin, had raised himself to the throne, passed the nine last years of his life in a private condition. Reason had dictated, and content seems to have accompanied, his retreat, in which he enjoyed, for a long time, the respect of those princes to whom he had resigned the possession of the world. It is seldom that minds long exercised in business have formed the habits of conversing with themselves, and in the loss of power they principally regret the want of occupation. The amusements of letters and of devotion, which afford so many resources in solitude, were incapable of fixing the attention of Diocletian; but he had preserved, or at least he soon recovered, a taste for the most innocent as well as natural pleasures, and his leisure hours were sufficiently employed in building, planting, and gardening. His answer to Maximian is deservedly celebrated. He was solicited by that restless old man to reassume the reins of government, and the Imperial purple. He rejected the temptation with a smile of pity, calmly observing, that if he could show Maximian the cabbages which he had planted with his own hands at Salona, he should no longer be urged to relinquish the enjoyment of happiness for the pursuit of power.
In his conversations with his friends, he frequently acknowledged, that of all arts, the most difficult was the art of reigning; and he expressed himself on that favorite topic with a degree of warmth which could be the result only of experience. "How often," was he accustomed to say, "is it the interest of four or five ministers to combine together to deceive their sovereign! Secluded from mankind by his exalted dignity, the truth is concealed from his knowledge; he can see only with their eyes, he hears nothing but their misrepresentations. He confers the most important offices upon vice and weakness, and disgraces the most virtuous and deserving among his subjects. By such infamous arts," added Diocletian, "the best and wisest princes are sold to the venal corruption of their courtiers."
A just estimate of greatness, and the assurance of immortal fame, improve our relish for the pleasures of retirement; but the Roman emperor had filled too important a character in the world, to enjoy without alloy the comforts and security of a private condition. It was impossible that he could remain ignorant of the troubles which afflicted the empire after his abdication. It was impossible that he could be indifferent to their consequences. Fear, sorrow, and discontent, sometimes pursued him into the solitude of Salona. His tenderness, or at least his pride, was deeply wounded by the misfortunes of his wife and daughter; and the last moments of Diocletian were imbittered by some affronts, which Licinius and Constantine might have spared the father of so many emperors, and the first author of their own fortune. A report, though of a very doubtful nature, has reached our times, that he prudently withdrew himself from their power by a voluntary death.
Diocletian, who, from a servile origin, had raised himself to the throne, passed the nine last years of his life in a private condition. Reason had dictated, and content seems to have accompanied, his retreat, in which he enjoyed, for a long time, the respect of those princes to whom he had resigned the possession of the world. It is seldom that minds long exercised in business have formed the habits of conversing with themselves, and in the loss of power they principally regret the want of occupation. The amusements of letters and of devotion, which afford so many resources in solitude, were incapable of fixing the attention of Diocletian; but he had preserved, or at least he soon recovered, a taste for the most innocent as well as natural pleasures, and his leisure hours were sufficiently employed in building, planting, and gardening. His answer to Maximian is deservedly celebrated. He was solicited by that restless old man to reassume the reins of government, and the Imperial purple. He rejected the temptation with a smile of pity, calmly observing, that if he could show Maximian the cabbages which he had planted with his own hands at Salona, he should no longer be urged to relinquish the enjoyment of happiness for the pursuit of power.
In his conversations with his friends, he frequently acknowledged, that of all arts, the most difficult was the art of reigning; and he expressed himself on that favorite topic with a degree of warmth which could be the result only of experience. "How often," was he accustomed to say, "is it the interest of four or five ministers to combine together to deceive their sovereign! Secluded from mankind by his exalted dignity, the truth is concealed from his knowledge; he can see only with their eyes, he hears nothing but their misrepresentations. He confers the most important offices upon vice and weakness, and disgraces the most virtuous and deserving among his subjects. By such infamous arts," added Diocletian, "the best and wisest princes are sold to the venal corruption of their courtiers."
A just estimate of greatness, and the assurance of immortal fame, improve our relish for the pleasures of retirement; but the Roman emperor had filled too important a character in the world, to enjoy without alloy the comforts and security of a private condition. It was impossible that he could remain ignorant of the troubles which afflicted the empire after his abdication. It was impossible that he could be indifferent to their consequences. Fear, sorrow, and discontent, sometimes pursued him into the solitude of Salona. His tenderness, or at least his pride, was deeply wounded by the misfortunes of his wife and daughter; and the last moments of Diocletian were imbittered by some affronts, which Licinius and Constantine might have spared the father of so many emperors, and the first author of their own fortune. A report, though of a very doubtful nature, has reached our times, that he prudently withdrew himself from their power by a voluntary death.