If you are going to be successful in providing professional service, in anything, you must believe that you can help anyone, if given the opportunity, and that you are worth far more money than they are spending on you. Your price must reflect your effort and skill, but it must make your client/customer say “I’m not going to tell them, but I would totally pay more.”
If you mention the possibility of raising your prices and they don’t bat an eye, you’re already there. Whether they are the best in the world at what they do or just an average hard working person you must feel that you can and will do a better job at improving them than they could do on their own and just as good or better than anyone else could do in helping them. Figure it out. Put in the time. Put in more focused effort.
If you have to ask how much effort or how long you’ll need to work you are still very far from good enough and shouldn’t even be thinking you’re great. The more difficult it will be for you to give the highest quality service the more time that you are going to have to spend in research and development. You’re just going to have to work harder than any other certified personal trainer or fitness professional, and certainly harder than your client does.
No one can say how hard and how long you’ll have to work at it, but if you don’t truly believe you’re worth every penny and more, or if they don’t say so, you aren’t working hard or long enough yet.