VATICAN CITY (AP) — Pope Benedict XVI basked in an emotional sendoff Wednesday from a massive crowd at his final general audience in St. Peter's Square, recalling moments of "joy and light" during his papacy but also times of difficulty when "it seemed like the Lord was sleeping."

An estimated 150,000 people, many toting banners saying "Grazie!" ("Thank you!"), jammed the piazza to bid Benedict farewell and hear his final speech as pontiff. In this appointment — which he has kept each week for eight years to teach the world about the Catholic faith — Benedict gave deep thanks to his flock for respecting his decision to retire.

Benedict clearly enjoyed the crowds, taking a long victory lap around the square in an open-sided car and stopping to kiss and bless half a dozen children handed to him by his secretary. A total of 70 cardinals, some tearful, sat in solemn attendance.

But Benedict made a quick exit, foregoing the typical meet-and-greet session that follows the audience; the Vatican has said there were simply too many people who would have wanted to say goodbye.

Given the historic moment, Benedict also changed course and didn't produce his typical professorial Wednesday catechism lesson. Rather, he made his final public appearance in St. Peter's a personal one, explaining once again why he was becoming the first pope in 600 years to resign and urging the faithful to pray for his successor.

"To love the church means also to have the courage to take difficult, painful decisions, always keeping the good of the church in mind, not oneself," Benedict said to thundering applause.

He noted that a pope has no privacy: "He belongs always and forever to everyone, to the whole church." But the pope promised that in retirement he would not be returning to private life — instead taking on a new experience of service to the church through prayer.

He recalled that when he was elected pope on April 19, 2005, he questioned if God truly wanted it. "It's a great burden that you've placed on my shoulders," he recalled telling God.

During his eight years as pope, Benedict said, "I have had moments of joy and light, but also moments that haven't been easy ... moments of turbulent seas and rough winds, as has occurred in the history of the church when it seemed like the Lord was sleeping."

But he said he never felt alone, that God always guided him, and he thanked his cardinals and colleagues for their support and for "understanding and respecting this important decision."

Under a bright sun and blue skies, the square was overflowing with pilgrims and curiosity-seekers. Those who couldn't get in picked spots along the main boulevard leading to the square to watch the event on giant TV screens. Some 50,000 tickets were requested for Benedict's final master class. In the end, the Vatican estimated that 150,000 people flocked to the farewell.

"It's difficult — the emotion is so big," said Jan Marie, a 53-year-old Roman in his first years as a seminarian. "We came to support the pope's decision."

With chants of "Benedetto!" erupting often, the mood was far more buoyant than during the pope's final Sunday blessing. It recalled the jubilant turnouts that often accompanied him at World Youth Days and events involving his predecessor, Pope John Paul II.

Benedict has said he decided to retire after realizing that, at 85, he simply didn't have the "strength of mind or body" to carry on.

"I have taken this step with the full understanding of the seriousness and also novelty of the decision, but with a profound serenity in my soul," Benedict told the crowd Wednesday.

Benedict will meet Thursday morning with cardinals for a final time, then fly by helicopter to the papal residence at Castel Gandolfo south of Rome.

There, at 8 p.m., the doors of the palazzo will close and the Swiss Guards in attendance will go off duty, their service protecting the head of the Catholic Church over — for now.

Many of the cardinals who will choose Benedict's successor were in St. Peter's Square for his final audience. Those included retired Los Angeles Cardinal Roger Mahony, the object of a grass-roots campaign in the U.S. to persuade him to recuse himself for having covered up for sexually abusive priests. Mahony has said he will be among the 115 cardinals voting on who the next pope should be.

Also in attendance Wednesday were cardinals over 80, who can't participate in the conclave but will participate in meetings next week to discuss the problems facing the church and the qualities needed in a new pope.

"I am joining the entire church in praying that the cardinal electors will have the help of the Holy Spirit," said Spanish Cardinal Julian Herranz, 82.

Herranz has been authorized by the pope to brief voting-age cardinals on his investigation into the leaks of papal documents that exposed corruption in the Vatican administration.

Vatican officials say cardinals will begin meeting Monday to decide when to set the date for the conclave.

But the rank-and-file faithful in the crowd Wednesday weren't so concerned with the future; they wanted to savor the final moments with the pope they have known for years.

"I came to thank him for the testimony that he has given the church," said Maria Cristina Chiarini, a 52-year-old homemaker who traveled by train from Lugo in central Italy with some 60 members of her parish. "There's nostalgia, human nostalgia, but also comfort, because as a Christian we have hope. The Lord won't leave us without a guide."