It would seem that it is a no-brainer that by improving your sales skills, you greatly improve your chances for career success. This is no secret, but many sales professionals get set in their ways and fall into the trap of not continually seeking new sales techniques to improve their sales skills.
This does not only apply to sales professionals, but if you think about it, everyone sells. Marketing sells their projects, finance sells their suggestions, HR sells ideas and the list goes on. For sales professionals, sales skills is the art and science behind what you do. I think most of the time, when sales professionals reach a point that they have achieved a level of success in their career, they ease up on their professional development and shy away from staying updated on different sales techniques.
The best sales professionals I have met, keep the sales skills blade sharp and continually find new and innovate ways to ask better questions, develop better relationships, learn their products and find ways to position their products/service to their customers. There are many great sales books available as well as audio-books to listen to while driving. The point is, continue to learn and never stop seeking to hone your trade and seek excellence in your craft. You will still be as effective as you are, but with improved sales skills, usually comes more sales and what follows is career success. Keep learning!