A modern biographer, Ron Chernow, concludes:

Alcohol was not a recreation selfishly indulged, but a forbidden impulse against which he struggled for most of his life. ... While drinking almost never interfered with his official duties, it haunted his career and trailed him everywhere, an infuriating, ever-present ghost he could not shake. It influenced how people perceived him and deserves close attention. As with so many problems in his life, Grant managed to attain mastery over alcohol in the long haul, a feat as impressive as any of his wartime victories. 2a

Like so many tobacco users, Grant gave up smoking when it was too late. Suffering chronic pain and diagnosed with an incurable oral cancer that was caused by tobacco, Grant was racing against his disease to finish writing his memoirs, so that his wife would not be destitute. Grant told friends on November 20, 1884:

Gentlemen, this is the last cigar I shall ever smoke. The doctors tell me that I will never live to finish the work on which my whole energy is centered these days... if I do not cease indulging in these fragrant weeds. It is hard to give up an old and cherished friend, that has been your comforter and solace through many weary nights and days. But my unfinished work must be completed, for the sake of those that are near and dear to me. 2b

He would die in nine months.

Yet, according to his adoring wife, he could lift 200-pound beams and could ride 50 miles in a day without breaking a sweat 2j.

It is also likely that Grant's illness contributed to his failures in life at that time 1a.

Comment: As Bumgarner recognized 1f, pleuritic plain after a protracted period in bed raises the possibility that Grant developed a blood clot in one of his legs. (The bedsores alone indicate the extent of his time in bed, and the "rheumatism" in his legs could have been the pain of a deep vein thrombosis, i.e. blood clot.) If the blood clot dislodged and traveled ("embolized") to his lungs, pleurisy could result.
    There is a second possibility. Given that Grant's cancer became symptomatic six months later, a blood clot in the lungs could have been a side effect of the cancer, a combination known as Trousseau syndrome. This can occur before a cancer becomes symptomatic. However, Trousseau syndrome seems less likely because there are no reports of later clots, which would be expected, and because Grant's tumor was "epithelial" rather than a mucin-producing adenocarcinoma.

This episode altered Grant. He continued to be stoical and uncomplaining, but "he had grown very old-looking ... and his face looked as though some great sorrow had befallen him," according to an acquaintance. By February he was moving about the house on crutches, still bothered by leg pain. 2p

Even into July (1884) he remained weak and lame, using crutches 2q. At least through October he was still using crutches 2b.

After discovering a suspiciously swollen area on the back of the tongue, Barker referred Grant to Dr. John Douglas, a throat specialist. Douglas, too, found a hard, swollen area on the back of the tongue and, using a mirror, saw three lesions on the roof of the mouth. Grant asked, "Is it cancer?" Douglas replied, "General, the disease is serious, epithelial in character, and sometimes capable of being cured" ("epithelial" being a euphemism for "cancer" in that era). Douglas lessened the pain by topical application of cocaine and swabbed away tissue debris and mucus from the area, recommending that Grant return twice daily for repeat treatments. He did this, for a time riding a public streetcar to and from Douglas's office, no doubt startling his fellow passengers with his presence. 2s

In Chernow's unforgettable phrase, "Gradually Grant was ground down into a mass of pain" 2b. After a severe attack of neuralgia, his dentist extracted three teeth without anesthesia; this facilitated Douglas's cleanings, but did not lessen the pain 2b.

In November an eminent pathologist, Dr. George Shrady, reviewed some tissue Douglas took from Grant's tumor and was "perfectly sure" that it was "a lingual epithelioma -- cancer of the tongue." He forecast that Grant would endure agonizing pain and die within a year. Shrady told Grant himself that he suspected a connection between Grant's smoking and his cancer, and advised Grant to smoke at most one cigar a day. Grant lost his taste for tobacco soon after, and gave up smoking (see above). 2t

What followed was tragic and triumphant. Grant had recently been swindled and was broke. To provide for his soon-to-be widowed wife, he resolved to write his memoirs for publication, racing against the cancer. Despite suffering unrelenting pain and harboring a baseball-sized tumor in his neck, for four to six hours a day he would sit and write in an overstuffed chair, his legs up, a wool cap on his head, and a muffler around his neck. When he could not sleep, he wrote. 2u

He reluctantly took opiates to ease the pain, but that slowed his work. Because swallowing magnified the pain, he went without water and food for extended periods, to swallow less. His valet applied hot compresses to Grant's head and sprayed his throat with numbing "cocaine water." To spare his family, Grant maintained a stoic face... during the day. 2v

Despite all this, Grant's output was phenomenal, in both quantity and quality. Although a man of lifelong taciturnity, Grant could produce 10,000 words of superb, lean prose in a day (that's 40 double-spaced typewritten pages). All told, he wrote 336,000 words in one year. 2w

By May 1885, he was forced to dictate. His friend and publisher, Mark Twain, described Grant "never pausing, never hesitating for a word, never repeating" as he dictated 9000 words describing Lee's surrender at Appomattox Court House -- in one sitting. The quality of Grant's writing astonished Twain. "There is no higher literature than these [memoirs]... Their style is flawless... no man can improve upon it." 2v

Grant died July 23, 1885 -- a week after finishing the manuscript. He weighed 90 pounds. He had already told a pastor, "I am ready to go. No Grant has ever feared death. I am not afraid to die." 2x

Twain thought the book had kept him alive for several months 2x. It was an explosive, record-setting best-seller, providing his wife the modern equivalent of $14 million 2y. Grant's memoirs are recognized today as the greatest presidential autobiography ever written -- and one of the greatest autobiographies written by anyone, anay time.