This affects quite a few speakers. They have a severe case of "I know I'm right!" and it doesn't matter who disagrees with them or what reasons they offer - any advice falls on deaf ears. Commitment is good; stubbornness is not.
How do you know the difference? For one, consider the source of the advice. If that person is considerably more successful than you are, then you should carefully consider their advice, no matter how much you may disagree with it. (This doesn't mean that you must follow their advice. But do give it careful consideration.)
Next, look into your soul and consider whether your conclusions result from your objections, or your objections result from your conclusions. In other words, have you already made up your mind? Are you coming up with any reason you can to justify what you've already decided? Or are you genuinely open to changing your mind?
Where do you find good advice? If possible, join (or form) a mastermind group. Your mastermind group will usually (but not always) be composed of other professional speakers at about your level of experience. Your group can be an invaluable source of good advice.
You should also start forming alliances with other professionals that you'll meet through professional associations. For example, you might want to join the National Speakers Association. If you're a trainer, you might want to check into The Association for Talent Development (ATD), formerly known as the American Society for Training & Development (ASTD). Toastmasters International is an invaluable organization for honing your platform skills. And of course, almost every industry has one or more industry-specific organizations; you should certainly investigate them.
Of course, you don't have to get your advice face-to-face. You can read books or research the Internet. But as I cautioned before, carefully consider the source of the advice before you consider the advice itself.
1. Try to join (or form) a mastermind group of several professional speakers at a similar level of experience.
2. Look into the qualifications required to join NSA or ATD. If you think they'd be beneficial to you, join and become active.
3. Look for local chapters of national organizations. They can provide more frequent (and more convenient) meetings.
4. Continue reading business books in general.
5. Business resources specifically created for professional speakers are harder to find, but this makes them even more valuable. When you find a source of good pro-speaker-wisdom, tap into it!