What ONE skill, if you developed it and did it consistently in an excellent fashion, would have the greatest positive impact on your career?

Communication skills

Creative thinking. 

I would like to be proficient in MS Excel.

Planning (in your personal and professional life) is the most crucial skill that we need in order to succeed with a big percentage of success also planning help us to set our goals so we can measure and move forward toward this goal. 

Perfection...

Communication

Time management

Begin with the end in mind. The skill for that is setting your goals (long term goals, & short term goals) correctly.

Learning

Leadership

I would like to master taking calculated risk , putting my fears aside and dive into a brand new project with zest, and navigate around the various challenges. I  feel I will learn alot.