VATICAN CITY — Even though human beings are weak and imperfect, Christians can't be lazy and wallow in sin, Pope Francis said.

Believing in God means making a real effort to live the faith fully, not superficially, and asking the Lord for help and strength to follow him on the path of holiness, he said in his morning Mass homily Oct. 24.

"We really are weak, and many times -- many times -- we sin, we have shortcomings," he said during the Mass in the Domus Sanctae Marthae, according to Vatican Radio.

The tendency to sin must be accompanied by acknowledging, "'Yes, I'm a sinner, I am weak' and always going to the Lord and telling him, 'Lord, you have the strength, but give me faith! You can heal me!'"

It won't work if people get comfortable with having a life where "I believe in Jesus Christ, but I live as I want," he said. "Uh no, that doesn't sanctify you, that will not work! It's a contradiction!"

The pope said God re-creates humanity in Jesus Christ.

If before Christ, "our whole life, our body, our soul, our habits were on the path of sin and wickedness, after this re-creation we have to make an effort to walk on the path of justice, of sanctification," he said.

With baptism, parents made an act of faith in their child's name, he said. That child must then go on to "take it up again," to take the faith and "carry it forward" with their lives.

Living the faith means taking it very seriously and doing what Jesus did: adore God -- "God is always first" -- help others, work for justice and give others hope.

If "we accept the faith and then we don't live it, we are Christians only by rote," he said.

If people don't empty their life for one filled with Christ, if they continue with the attitude of "I call myself Christian, but I live like a pagan," then they are "lukewarm Christians" who pick and choose, who are, "as our moms would say, 'wishy-washy Christians,'" he said.

There has to be "a true conversion" inside, the pope said, not just a veneer of faith, where the catechism is brushed on like "a bit of paint."

People have to "let go of everything that distances them from Jesus Christ," he said, and "make everything new; everything is new in Christ."

"You can do it!" he said.