You have heard that it was said, "An eye for an eye and a tooth for a tooth." But I say to you, Do not resist the one who is evil. But if anyone slaps you on the right cheek, turn to him the other also. And if anyone would sue you and take your tunic, let him have your cloak as well. And if anyone forces you to go one mile, go with him two miles. Give to the one who begs from you, and do not refuse the one who would borrow from you.
—Jesus Christ (Matthew 5:38-42, ESV)
Here is one of Jesus' most impractical teachings. So impractical, in fact, that the commentary in my ESV Study Bible advises, "In the case of a more serious assault, Jesus' words should not be taken to prohibit self-defense", and "[Christians] are not required to give foolishly or to a lazy person who is not in need". The grown-ups who wrote the ESV Study Bible could obviously see, by innumerable examples in history and the news, that people who take Jesus' words seriously tend to get crucified. And in their estimation, crucifixion is failure.
But the Kingdom of God is no place for grown-ups:
I thank you, Father, Lord of heaven and earth, that you have hidden these things from the wise and understanding and revealed them to little children; yes, Father, for such was your gracious will.
—Jesus Christ (Matthew 11:25-26, ESV)
Let the children come to me, and do not hinder them, for to such belongs the kingdom of God. Truly, I say to you, whoever does not receive the kingdom of God like a child shall not enter it.
—Jesus Christ (Luke 18:16-17)
Jesus, who chose the foolish and weak things to shame the wise and strong, proclaimed a new kingdom in which the world's terms of success and failure are radically redefined. In his coronation ceremony, he was crowned with thorns and hung on a cross, a success in the eyes of God and an utter failure in the eyes of the world.
The early church understood his topsy-turvy reconfiguration of values: After being flogged, the apostles "left the presence of the council, rejoicing that they were counted worthy to suffer dishonor for the name." (Acts 5:41) The early Christians were often arrested, flogged, and martyred, taking any number of "more serious assaults" without retaliation or even self-defense. Had the early Christians been as sensible as the writers of the ESV Study Bible, they would have seen the impracticality of their strategy in the face of evil. But unlike those writers, and unlike perhaps the vast majority of Christians today, the early Christians operated not on practicality but on faith in Christ.
Insistence on worldly success (wealth, recognition, safety, and even survival) is, for a professing follower of Christ, a sin caused by faithlessness. The Body of Christ (that is, the Church) is meant not to affectionately ponder Christ at a distance, but to take up crosses and follow him - to crucifixion. The ecclesiastical Body is meant to freely offer itself up to death just as did the historic physical body of Christ.
At first glance, this is a depressing thought. True faith in Christ always leads away from comfort, often into suffering. At second glance, it is still a depressing thought. But, here is the hope: In Christ, in love, there is no failure. Following the ways of the world, success is always fragile and temporary, like the house built on the sand. But following Christ, failure is impossible - and success eternal, like the house built on the rock. Just as Christ triumphed on the cross, just as the early church triumphed in persecution and martyrdom, we are guaranteed heavenly triumph regardless of any worldly failure (poverty, disgrace, danger, and even death) insomuch as we have the faith - foolish, childish faith - to follow Christ.