I very recently had a discussion with a guy who was adament that he could defend against knife, stick and bottle attacks after watching an instructory video.
The problem is that in real life people do not always act the way the videos show.
he suggested moving off line in defence against a base ball bat. I have ortunately ( or unfortunately) been in this situation once. i got relatively hurt, but the other guy was a little worse off. What did it prove...... that knowledge and training are the keys, BUT that nothing substitutes a real situation. I teach knife defence, stck defence and bottle defence in my classes. Slowly at first, then a little faster.
After several months of boring reps the drill becomes almost natural. then we can do it with dimmer lights loud music and most importantly an unknown attck.
Some people think that learning from books and videos is the easy way out.
My opinion is that a little knowledge is a very dangerous thing. It leads påeople into a false sense of security. In the real world, against a base ball vat, you will likely get hurt but survive.
F*** up against a knife..... you are likely dead.
My advice, learn from a school. When you have a high grade use videos to compliment what you already know. trust you instructor and not video.
try also to get to know how the mind of a thug works. This is the study of an art, not wearing a different coloured belt every 6 months. this shows physical competrance, and not always mental.