No one likes to discover that what they've been doing for the past 10-20 years is a lie. So imagine if you've been training that long and suddenly someone shows you something that makes sense of everything that you thought was missing.
So what do you do now? Quit? Give up? Throw a fit of anger? At the end of the day, you get what you sow. So even though you've done something 'wrong' the past 10-20 years, if you have trained with at least some common sense and with an objective in mind, you would be much better off than someone who hasn't train that long. Yes someone with a better training method would be better off than you and nothing you do can change that, but it doesn't detract from the fact that you now have a higher base to start training the correct way than if you were to start from zero entirely.
Also, it is quite possible that this new revelation might be actually more positive for you than you really thing. At this point in time in your training, you probably would have thought you know most of what you need to know. Its like a seasoned veteran who don't really pay much attention to minor details anymore and instead focuses on getting the job done, sometimes improperly or with more force than necessary. By starting again using unfamiliar methods, you will perform your techniques with a beginners mind. Conscious of trying to do the right thing. At the sametime you are also reinforced by the knowledge and experience you have garnered over the years.
Life is a journey. There is no ultimate ending nor was there a real beginning. So why create titles for knowledge which has no boundaries?