ROME (CNN) -- In front of rapt crowds, Pope Benedict XVI spoke of moments of joy and struggle Wednesday during his final public address from a stage set up in St. Peter's Square.
Dressed all in white and looking serene, the pope used his last general audience to call for a renewal of faith and speak of his own spiritual journey through eight years as leader of the world's 1.2 billion Catholics.
As he finished, cheers erupted from the tens of thousands gathered in the square -- acknowledged by Benedict with an open-armed embrace.
As well as calling for a renewal of faith, he used his last general audience to discuss his experience as pontiff and his almost unprecedented decision to abdicate the role starting Thursday.
Benedict recounted how when he was asked to be pope eight years ago, he had prayed for God's guidance.
"And the Lord has really driven, I was close, I could feel his presence every day," he said.
"It was a part of the journey of the Church that has had moments of joy and light, but also moments that were not easy."
The Church is like a boat that passes through stormy seas, but God will "not let her sink," he said.
He thanked the cardinals, the clergy in Rome, Vatican officials and priests worldwide, as well as their congregations, saying "the heart of a pope extends to the whole world."
He had taken the step of resignation well aware of its seriousness and novelty, but also "with a deep peace of mind," he said.
"In recent months, I felt that my strength had decreased, and I asked God earnestly in prayer to enlighten me with his light to make me take the right decision not for my sake, but for the good of the Church," he said.
"Loving the Church also means having the courage to make tough choices," he said, as he called on the faithful to pray for him and the new pope.
Benedict gave an insight into the life of the pontiff, describing it as without any kind of privacy, with his time devoted entirely to the Church -- perhaps particularly difficult for a man known for his love of scholarship.
His life in retirement will be "simply a return to the private place. My decision is to forgo the exercise of active ministry, not revoke it. In order to return to private life, not to a life of travel, meetings, receptions, conferences and so on," he said.
Vatican officials said 50,000 tickets had been handed out for Benedict's last general audience -- but authorities said they had prepared for as many as 200,000 people to show up to witness the historic moment in person.
Benedict, who spoke first in Italian, also gave greetings in French, German and English, among other languages, reflecting the Church's global reach.
Those lucky to have tickets listened from seats in front of St. Peter's Basilica. Among them were many of the Roman Catholic Church's senior clergy.
Others packed around the edges of the square and surrounding side streets, hoping to catch a final glimpse of the pontiff.
Among the crowds are groups of pilgrims, who've traveled to Rome for the special and emotional occasion, as well as local residents and curious visitors keen to share in the moment.
Standing in the open, glass-topped vehicle, the pope waved as he slowly made his way along pathways through the crowds. Some waved flags and banners as they stood under cold but clear skies.
Normally in winter, the pope would give his weekly Wednesday general audience inside a hall within Vatican City, but the event was moved outside because of the anticipated huge crowds.
The pope won't give the usual brief personal greetings to people afterward, but will meet delegations of heads of state in Vatican City later.
Benedict, who stunned the world's Catholics when he announced his resignation just over two weeks ago, will leave office at 8 p.m. local time Thursday.
At that point, a transition period will begin, as around 115 cardinals gather in Rome to pick a successor in a secretive election known as a conclave.
The Vatican has been rewriting the rules to cope with an almost unprecedented situation -- Benedict is the first pope to resign in nearly 600 years.
He will meet with the cardinals Wednesday and Thursday, before being flown by helicopter to the papal summer residence at Castel Gandolfo.
There, from a balcony, he will greet the crowds one last time before his resignation takes effect and the Swiss Guards, who by tradition protect the pope, ceremonially leave the residence's gate.
More details were given Tuesday of how the 85-year-old's life in retirement will play out.
He will keep the papal title Benedict XVI, rather than reverting to the name Joseph Ratzinger, and will be referred to as "his holiness," Vatican spokesman the Rev. Federico Lombardi said.
He will also go by the title his holiness "Pontiff emeritus" or "Pope emeritus."
Living out of the public eye in a small monastery within Vatican City, Benedict will wear a simple white robe, without the papal red cape, and will swap his red shoes for brown ones. He is expected to devote his time to prayer and study.
Vatican officials have said they don't anticipate any interference from Benedict as a new pope takes office.
However, his influence will be felt in as much as he appointed 67 of the cardinals who will enter the conclave.
Whoever his successor may be will have plenty on his plate, from allegations swirling in the Italian media that gay clergy may have made themselves vulnerable to blackmail by male prostitutes -- a claim vehemently denied by the Vatican -- to the festering issue of the Church's handling of child abuse by priests.
Meanwhile, the cardinals who must elect the new pope are already gathering in Rome, Lombardi said.
The dean cardinal will on Friday summon the cardinals to a general congregation, Lombardi said. That could come as soon as Monday, although the date is not yet fixed.
The cardinals will then decide exactly when to hold the conclave, during which they vote for the new pontiff.
Special prayers will be said during the "sede vacante," or empty seat period, seeking guidance for the election of the new pope. The cardinals will lead the prayers.
After his resignation, Benedict -- who cited the frailty of age as the reason he resigned -- will no longer use the Fisherman's Ring, the symbol of the pope, Lombardi said. The ring will be destroyed, along with Benedict's papal seal, after his departure from office.
CNN's John Allen contributed to this report.