Photo: The Canadian Press. All rights reserved.

Pope Benedict XVI waves to pilgrims in St. Peter's Square at the Vatican, Wednesday, Feb. 27, 2013. Pope Benedict XVI greeted the Catholic masses in St. Peter's Square Wednesday for the last time before retiring, making several rounds of the square as crowds cheered wildly and stopping to kiss a half-dozen children brought up to him by his secretary. (AP Photo/Luca Bruno)

Pope Benedict XVI bid an emotional farewell Wednesday on the eve of his retirement, recalling moments of "joy and light" during his papacy, but also times of difficulty when "it seemed like the Lord was sleeping."

Some 150,000 people, many waving banners proclaiming "Grazie!" flooded St. Peter's Square, eager to bear witness to the final hours of a papacy that will go down in history as the first in 600 years to end in resignation rather than death.

Benedict basked in the emotional send-off, taking a long victory lap around the square in an open-sided car, and stopping to kiss and bless half a dozen babies. Seventy cardinals, some tearful, sat in solemn attendance, and gave him a standing ovation at the end of his speech.

Benedict then made a quick exit, forgoing the meet-and-greet session that typically follows his weekly general audience, as if to not prolong the goodbye.

Given the weight of the moment, Benedict also replaced his usual Wednesday catechism lesson with a heartfelt final address, explaining once again why he was retiring and assuring his flock of 1.2 billion that he was not abandoning them.

"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 pontiff has no privacy, neither as pope, nor in his future role as emeritus pope: "He belongs always and forever to everyone, to the whole church."

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."