Coaching is a powerful management tool, but the reality is not everyone can be coached.

If you’re not willing, or able, to objectively look at your own thinking, behaviour and actions, then coaching may have limited impact.
If you’re not willing or able to take personal accountability for your commitments, then even the best coach in the world will not be able to help you succeed.
A big part of the coaching and development process is getting feedback, often a lot of it. Some of it will certainly be critical, and at times it will be difficult to hear. Your ability to take things in your stride will determine if you are able to gain insight or if you close up and get defensive.
People who are willing to ask why, and then why again, and then why a few more times, are much more likely to find root causes and make fundamental changes to the way they behave and think.
So be honest with yourself before you hire anyone. The simple truth is that it is no criticism of anyone. It just means the timing or the mindset is not right yet. If you are curious about what working with a coach looks like, have a read of what a business coach actually does, or take a look at this general overview. The owners who get the most from it are the ones who arrive curious, accountable and ready to hear the hard truths.