It may be hard to grasp, but you want to get as close as possible to the hand with the weapon. Once you close the gap between you and your attacker he can no longer use momentum to increase the damage. Next, fight to restrain that hand! Use whatever means necessary to distract him from using that weapon. First choice is always to attack the eyes. Next a few sharp head bunts using the top of your head are always a good move; try to aim for the face.
You can also run your foot hard down the front of the shin bone- that stings. Drive your heel into his instep, an elbow across the face, or the top of your knee into the outside of his thigh. Never try to strike with a fist; the power is not half that of an elbow strike. Avoid cheap shots to the groin; it takes too long for the pain to register-two to five seconds- and will in fact encourage a greater aggression and renewed strength
If all of these options have failed and you can't disable him, or get the weapon away, then start biting. Gnaw a hole right through his hand or arm or whatever body part is closet. This is a last resort because of blood-transmittable diseases, but it is effective.
For Yourself and Your Home
Our instructor advised us to always have a weapon on hand or nearby. He called them the great equalizers. Now when he said weapons, he didn't necessarily mean a knife or gun. If you're in a parking lot; place keys between your fingers, the ends pointing outwards. Use metal nail files, they go through skin too. At home purposely leave things like golf clubs, broom sticks, bats, baseballs, harsh chemicals, in places where only you are aware of them. (Please keep in mind the safety of young children in the home-be smart about where you leave things). Be sure to lock your garage and sheds. Don't invite someone to break into your home by leaving tools in the yard for them to use.
Make plans with your family. What will you do if someone breaks in? Is there a "safe room" to go to that has a secure line or a cell phone easily accessible? Have you considered a home alarm system? Are your yards free of trees and bushes that block visibility from the sidewalk and driveway or allow good hiding places in the dark? I know in the city we all want privacy from our neighbors, but the more people can see of your house, the more likely an intruder will be spotted. These are all little things we often think of too late.
Think About It
The odds of having to confront an attacker in a struggle for your life are less than 3%. A comforting thought is that most attackers will stop if you fight back. They are looking for easy prey and hope that the fear of what is happening to you disables you. Remember an adrenaline rush is not permanently incapacitating, it is natural and will give you strength.
There are many different self-defense classes and courses that teach you how to keep yourself safe. As with any skill, a mental understanding, visualization, and physical practice help engrain the knowledge in our brains so we can recall it when we need it most. But when the clock is ticking and how many seconds of life are left depend on you being capable of disabling your attacker, these RAT techniques are highly effective and meant to save your life. Knowing how to defend yourself and never having to use your knowledge, is better than wishing you knew when it's too late.