I believe you should use most of your time and energy focusing on your strengths. However, leaders must reserve some time to improve their weaknesses.  

The first step in any improvement is awareness. It is difficult, if not impossible, to improve weaknesses if you are not aware of it. Seeing yourself in action or paying close attention can help you identify your weaknesses. Getting honest feedback from those you respect is a gift, so receive feedback with an open mind. However, if you receive a singular piece of feedback from someone, verify it with others as well since feedback is subjective.