When you have walked the walk, People are more receptive to your counsel.
A course, a book, an experience, does not make an expert. There is something to be said about tried and true. You become more relatable when you have gone through the battles, you have experienced the heart ache, you have won, then lost it all, then won again. There is a strength of wisdom and experience that carries weight.
There’s also a level of Integrity when what you preach, you practice to the fullest. I don’t see how anyone would want to listen under any other circumstance.