But on the eve of what doctors described as a minor operation to repair a hole in his heart, the 77-year-old leader took ill again on Wednesday and was rushed by ambulance from his ranch in southern Israel to a Jerusalem hospital.
This time, the diagnosis was far more serious: a hemorrhagic stroke - the bursting of a blood vessel in the brain.
Sharon, a former general who has long seemed invincible to his countrymen, was rushed into emergency surgery.
Sharon has been prime minister since 2001, guiding Israel through a five-year Palestinian uprising, and opinion polls after last month's stroke continued to show him the clear favourite to win a March election as head of a new centrist party after quitting his rightist Likud movement.
Political analysts said no figure had dominated Israel to the same extent as Sharon since founding Prime Minister David Ben-Gurion.
"The moment he goes, everything will change"
Shmuel Sandler of Bar-Ilan University
"The moment he goes, everything will change," said political scientist Shmuel Sandler of Bar-Ilan University.
Israeli commentators were quick to point out that Palestinian leader Yasser Arafat, Sharon's long-time arch-foe, was two years his junior when he died in a Paris hospital last year just weeks after falling sick.
Sharon has had to endure one of the most pressure-filled years of his long career. There have already been signs it was taking its toll, with the prime minister sometimes looking drawn.
The source of much of the upheaval was the Gaza withdrawal Sharon engineered last year despite fierce opposition from hardliners within his own Likud party. It was Israel's first removal of settlements on land Palestinians want for a state.
Once the pullout was complete, Sharon opted to break away from Likud to form the Kadima Party, saying he no longer wanted to have his hands tied in pursuing his diplomatic strategy for ending conflict with the Palestinians.
Not long ago, the notion that the one-time champion of Israel's settlements would tear down part of his own project was unthinkable.
But it was a typically bold move by Sharon, who as an army commander had a legendary record for battlefield victories but also for defying the military top brass.
Sharon drew Arab enmity for masterminding the 1982 invasion of Lebanon, during which Christian militia allies massacred Palestinians in two refugee camps, and later for his crushing response to a Palestinian uprising that erupted after he visited a sensitive Jerusalem shrine in 2000.
But Sharon has won international accolades for ending 38 years of Israeli military rule in Gaza, though he has vowed never to relinquish much larger settlements in the occupied West Bank.