Put all of your skills in three categories: A, B, and C . Assuming you have ten hours a week that you could spend developing your skills. In ten hours you could take a C skill to a B- or you could take an A skill to an A+. Which one, the A+ or the B- skill, will have a greater impact on your business? The only time I suggest you focus on developing your weaknesses is if you have a debilitating weakness.
For example, I’m basically a C player when it comes to technology, but I’ve invested time in learning about podcasts, blogging, and websites, because those are critically important to my business.
If you are a C level public speaker and public speaking is critically important to your function, then I encourage you to improve that weakness. However, if you’re a “C” at spreadsheets and you have a highly competent assistant, then I don’t encourage you to take a computer class just to improve your skills.