Pope Benedict XVI made his final public appearance in St. Peter's Square a personal one on Wednesday, explaining once again why he was becoming the first pope in 600 years to resign and urging the faithful to pray for his successor.

The pope basked in an emotional send-off from an estimated 150,000 people at his final general audience, recalling moments of "joy and light" during his papacy and also times of difficulty when "it seemed like the Lord was sleeping."

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.

- Pope Benedict XVI said to thundering applause

The crowd, 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 thanked his flock for respecting his retirement, which takes effect Thursday.

Benedict clearly enjoyed the occasion, 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. Seventy cardinals, some tearful, sat in solemn attendance — then gave him a standing ovation at the end of his speech.

Benedict made a quick exit, foregoing the typical meet-and-greet session that follows the audience as if to not prolong the goodbye.

Given the historic moment, Benedict also changed course and didn't produce his typical professorial Wednesday catechism lesson. Rather, it was personal.

"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 he 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 he had 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."

The pope's eight-year tenure has been beset by the clerical sex abuse scandal, discord over everything from priestly celibacy to women's ordination, and most recently the betrayal by his own butler who stole his private papers and leaked them to a journalist.

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. About 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.

Based on reporting by the Associated Press.

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