"In the slow decline of my physical strength, internally, I am on a pilgrimage to the House (of the Lord)", Joseph Ratzinger wrote in a letter published in the Corriere della Sera daily, which had told him many readers were concerned about his health.
The former pope, who will turn 91 in April, said he was moved that "so many readers want to know how this last period of his life is going".
"It is a great grace for me to be surrounded, in this last point of a sometimes tiring path, with affection and kindness that I would not have imagined," Benedict added.
Since his resignation five years ago, the German-born pope has been living in a small monastery in the Vatican, with four nuns and his personal secretary Georg Gaenswein.
Two years ago, Mr Gaenswein reported that Benedict was "going out like a candle, slowly and serenely".
Benedict celebrates mass every day, prays a lot, receives visitors in small numbers and responds to many letters.
He also listens to television news in the evening and reads several Catholic newspapers as well as theology publications.
A senior member of the Vatican clergy said last year that the pope emeritus "no longer has the control of his hands, he can no longer play the piano, he sees very badly, but he has perfect lucidity, he remembers everything".
In 2013, Benedict became the first head of the church to resign in seven centuries, amid speculation he was on the verge of a nervous breakdown, unable to cope at the top of an institution beset by scandals.