All Christians "even the most saintly" do something "bad" every day, but we can learn to be better people by doing good deeds, Francis told Catholics on Tuesday.
"We all do something bad each day," Francis said in a homily as he celebrated mass at the Vatican's Santa Marta hotel.
"The Bible tells us that even the mostly saintly sin seven times a day," he stated.
During Lent - the 40-day period of fasting, prayer and reflection that leads up to Easter - Christians should "distance themselves" from evil by learning to do good, Francis said.
"It's not easy to do good. We always need to learn how. And The Lord teaches us," he said.
Like children, Christians need to learn "every day" along the road of life, Francis stressed.
Spiritual conversion does not happen by "going to a fairy who waves a magic wand", he said.
"Learning to do good through concrete acts is a journey... that takes courage and humility," he continued.