But I say, do not resist an evil person! If someone slaps you on the right cheek, offer the other cheek also.
In this passage, is Jesus telling us we're not allowed to defend ourselves? It would sure seem that way. So if someone is punches you and you fall to the ground and they keep punching you without ceasing, you are to lay there and take it even if it kills you!
Okay, of course that's not what Jesus is saying. His "turn the other cheek" message is more to do with retaliation and revenge than defending yourself. If someone hits you, don't hit them back. There are other ways to defend yourself that doesn't involve violence. Got Questions explains that Paul used a nonviolent form of self-defense when the Roman Empire was getting ready to flog him.
As The Gospel Coalition says, violent self-defense would be a last resort. They also point out this:
But if I am casting out demons by the power of God, then the Kingdom of God has arrived among you. For when a strong man is fully armed and guards his palace, his possessions are safe—
That sounds like you are meant to be prepared to defend yourself and your proper--
until someone even stronger attacks and overpowers him, strips him of his weapons, and carries off his belongings.
...okay, that feels like it's referring to demonic or spiritual self-defense as opposed to physical self-defense. Which is equally as important, if not even more so.
So is it okay for a Christian to defend themselves? It sounds like we're meant to use non-violent means to defend ourselves and only use violence when only necesary.
“But now,” he said, “take your money and a traveler’s bag. And if you don’t have a sword, sell your cloak and buy one! 37 For the time has come for this prophecy about me to be fulfilled: ‘He was counted among the rebels.’[a] Yes, everything written about me by the prophets will come true.”
38 “Look, Lord,” they replied, “we have two swords among us.”
“That’s enough,” he said.
This sounds like Jesus wanted them to be able to defend themselves without overarming. Have the ability to defend themselves, but not use it unless needed. Basically, if they are being repeatedly punched on the ground and the other person pulls out a knife and raises it. Even then, I take it it's best to not actually try to kill your attacker. When Peter cut off the ear of the Roman soilder, Jesus scolded him because that wasn't necesary.