The physical capascity to defend ourselves is a question of muscle memory, and partner training. Can it be done with a book, a DVD, etc. certainly. What such methods will lack entirely however are other people. We need big, small, fat, gigantic, old, young training partners to learn several things that videos, books cannot teach on the physical level.
The most critical component of self protection as you say is NOT putting ourselves in situations/places where trouble is likely to be found. Avoiding the avoidables
A very large friend, was an auto mechanic. Insanely strong. Every week, every few weeks he would open up with a new story of his latest 'trouble' he had with a women, at a bar, in the city, or with friends. They were absolutely incredible stories...
"...Midgets, diners and cops..." we loved to call his stories. Most times he would put on his "white hat" and play the role of "sheriff" (ie protecting somebody he thought needed it). A crazy girlfriend, or some damsel in distress would start a literal fight with somone at a diner, bar etc. He would get involved. There was always something, typically in places there should not have been possible to have any trouble. Church
Finally one day one of us asked him hey Al (made up name) you ever considered getting a new bunch of friends to go out with?
Once he figured it out, stop attending the bars where the blood always flew... stopped playing "sheriff"... he stopped having most problems.
Now the PROBLEM with "free seminars" becomes lack of an engrained response. I can learn all kinds of things at seminars, but unless I practice making that sushi an insane amount daily for months, it will never become the habit, we require at critical moments. Spend 3, 6 months doing something until it becomes habitual you have a technical base, a developed skill to work from.
Different bodies, different temperments are necessary as training partners. Self restraint is a critical skill of training. Starting out breaking our training partners is not a good idea.
What do we pay for that knowledge... time, often money. How much of either depends a lot on the person. How effective... in the papers all the time. 90 year old grandmother kills attacker, three teen thugs attack the wrong person... however such situation specticles are unfortunate. Standing over the bodies of an assailant is not required.
Protecting ourselves then running away (IMHV) a much smarter approach.
Merely my opinion, I could surely be mistaken,