It really should not be attempted by someone who feels any insecrurities, or lacks confidence. The horse will sense it and use it to his/her advantage.
If you are new to training, or even wanting to 'work' with your horse on something, it would be helpful to attempt the method on an older, more fogiving horse. I did that when I wanted to teach our mare to ground driving, but I had never done it, only seen it done. It helped, when I was ready to train the green mare, I was far more confident. I would definitely seek help from someone you admire that has good results with horses, I did that as well, before I attempted to train my first horse alone. (Now I just have trained my hubby's horse, and he was so impressed he thinks I should do it professionally.)
Many times it is the rider that is the root of the problem, and that should be explored as well as the horse's behavior.
And I have been seriously in danger, but I have learned to predict what the horse is going to do and I am pretty quick on my feet. But if you are going to try to solve an issue with yourself, it would be a good idea to know what you may be getting into. Horses themselves are dangerous, but training crosses into a territory of danger beyond just ridin (like that isn't dangerous enough!), and one you are voluntarily putting yourself in.