In his first public appearance since announcing his resignation, Pope Benedict XVI said he had felt "almost physically" strengthened by the love and prayers sent his way from Catholics and well-wishers.
He began his weekly general audience at the Paul VI Hall in the Vatican with an address in Italian, in front of a crowd of around 700 people.
He began, “Dear brothers and sisters, as you know.." but was swiftly interrupted by a loud round of applause, according to the Catholic News Service.
He continued: " As you know, I decided to renounce the ministry that the Lord entrusted to me April 19, 2005.
"I did this in full freedom for the good of the church after having prayed for a long time and having examined my conscience before God, well aware of the seriousness of that act, but also aware of no longer being capable of fulfilling the Petrine ministry with the strength that it requires.
"The certainty that the church is Christ’s and he will never cease guiding it and caring for it, sustains me and enlightens me. I thank all of your for the love and prayers with which you have accompanied me."
He acknowledge the difficulty of his decision to resign, rather than continue until death, like his predecessor John Paul II. "I have felt, almost physically in these days — which haven’t been easy for me — the strength that prayers, love for the church and prayers for me bring me.
"Continue to pray for me, for the church, for the future pope.”
Later on Wednesday the Pope will attend his last public Mass, for Ash Wednesday, in St Peter's Basilica. The location for the Mass has been moved from the small Sant' Anselmo church, to accomodate large crowds.
A new Pope is expected to be chosen by the end of Lent, in six weeks time.
Vatican spokesman Federico Lombardi said: "It will be an important concelebration, and the last led by the Holy Father in St Peter's."
He will hold one more Wednesday audience on 27 February, again in St Peter's Square, the day before he retires.