Yes, you can defend yourself, always. Otherwise, why didn't Jesus let Himself be murdered countless times when they sought His life? Why didn't the disciples, either the 70 or the 12? Why didn't Paul?
The phrase turn the other cheek also refers to accepting insults, and it only applies when you are preaching. See Ecclesiastes 3 also. The Devil would like it if you sat there and let yourself get beaten or killed, that's what he gets up for in the morning.
As Patriot pointed out to, if you are in the marriage covenant, then you are under direct obligation to God to physically protect your wife to any cost (including the life of any fool trying to attack her), and conversely, you must destroy anyone trying to attack you, for otherwise you again violate your marriage covenant, for then you rob your wife of you. Same with your children.
As always, plead the blood of Jesus, and trust in and declare God's promises of protection in Psalm 91, 103, 23 etc.