Bill Porter had an obvious weakness compared to other salesmen. But his sheer determination and persistence allowed him to push forward and turn his weakness into his strength. No one could have ever predicted him being the top seller of the company. This is the best thing about greatness. You never know where it is going to emerge. If Bill Porter can train himself to be the best at what he did, what is holding you back? You are not lacking the ability. You are blocking it.
If someone asked you what you could bring to the table if they took away what you did best, how would you answer? Start turning your weaknesses into your strengths and watch what you are able to achieve.