You will never have all the knowledge, so go with it!
One of the absolute BEST things to do with horses is to embrace the fact that you will never know all there is to know. Not only embrace it, own it, take it into yourself and NEVER forgot that you won’t ever have all the answers. The minute you think you do, you’re done, for there will always be another horse that will flummox you.
It's quite hard in the horse world to say “I don’t know” never mind actually accepting that idea, and saying it out loud in public. But I truly believe you will be a better horseman, and earn the respect of other reputable horse folks, by acknowledging just that. If you're already a professional, try “Let me look into that for you” .If you are just a few years into horses, listen and absorb all you can. Not everything you hear will be correct, and I have attended clinics where all I learned was how I will NEVER do something, but it's all learning.
There will be many people in the horse world that want to tell you what to do, and how to do it. It will be hard to know who to believe, but accepting that you don’t have to be an ‘expert’ in a few short years, will keep you open to learning.
One of our programs here at the farm has, I believe, stopped many people from buying a horse. People in the horse industry might not be so happy about that, but from where I’m standing in the rescue world, what I see is one less horse that will need a home in a couple of years, that will also come with a load of behavior (training) issues. What I DO want is for people to find a reputable professional that they like and trust, and go about learning all they can about horses, horsemanship and the riding discipline of their choice, BEFORE they buy their horse.