Managers do need to appreciate their strengths. If they don't, they could waste time and effort attempting to get better at leadership competencies they have already mastered. Or they could fail to leverage core capacities that would help them be more successful.
On the other hand, certain skills relied upon too heavily can become weaknesses. Being overly decisive, for example, can lead to the impression of arrogance.
Your strongest asset may be your analytical ability and attention to detail. But building and managing relationships may be the more critical skill as you take on a broader role. If that is a weak point for you, you can't afford to ignore it.