Teach what you know, not what you've heard.
The best teachers are the ones who have actually experienced what it is they are teaching. Anybody can be book smart, but to have actual experience on a certain topic or subject matter is where true knowledge lies. And this is in no way, shape or form meaning to discredit any teacher out there. There are some amazingly astounding teachers and professors!
Think about it...you go to a gym and want to hire a personal trainer in order to lose weight. Which trainer do you feel you would benefit from more? The one who has attended a few diet and nutrition classes as well hearing how the human body and all the science behind how the muscles work, but they personally have never been overweight their entire life and don't have to even work out to maintain their healthy body weight? Or what about the trainer who has spent years of their life as an obese person, has struggled with trying every diet out there, has learned how to fight off food temptations, has changed their mindset and exactly what sort of dedication, blood, sweat and tears it takes to get emotionally and physically fit and how to maintain that lifestyle?
Well, I think the later of the two has the experience, knowledge and understanding people struggling with being obese and overweight can relate to. Not to say there wouldn't be some advantage to hiring the first trainer, but can they really understand and relate how to help a client who feels in such deep despair they don't even know where to begin? I believe most people would want a trainer who has walked the walk, and not one that just talks the talk. This trainer KNOWS, to their core what self-loathing and feelings of despair being obese can lead to, and they also KNOW what it takes to help a client to pull themselves up out of those depths of despair. The first trainer may be able to share some valuable information, based upon what they have heard other trainers share with their clients, but I'd rather see an old photo album showing the struggles and progress they made, than a certificate of training in a pretty frame on the wall.
I want the "been there, don't that" method of teaching. I want someone that will comprehend my struggles and be able to provide real life relatable solutions, simply because they have been there, they have done that! I don't want someone to just teach me what they have heard. To get the most value out of someone else's experience, find the person that has the experience and will teach you what they KNOW.