I spend a lot of time with sales people talking not only about sales activity and skills but attitude. It is easy to under estimate the impact of attitude, emotional maturity, etc on the success of individual sales people. We in management rarely look at the emotional state of our employees, their maturity, etc simply hoping that the individuals have the requisite maturity and we can focus on the skills and results. Worst case fire the individual if they don't work out, its a lot easier than dealing with the difficult issues. Many managers believe that even further its none of their business or responsibility. I would propose this is a very short sighted view of your obligations to your company and your employees. Managers are not require just to produce short term results but also to build the capacity of the organization. And if you are not looking at the whole picture you are not doing your job.

Yet we don't have time or the qualifications to be therapists, the struggle is in the quest to find the happy medium. I think the crux of the issue is to support the person who is doing the job. In recognizing and identifying strengths and weakness in the sales person do not fail to identify areas where attitude or even emotional baggage might impede the rep in being successful. I do not propose necessarily discussing these things directly with the individual as unless you have a great relationship with the person it may be misconstrued as meddling. Rather try to implement techniques that can help address the behavior in a work context, and inevitably those habits will appear in other parts of their lives. Perhaps an example would be illustrative:

There are many reps who have self confidence issues. This behavior can manifest itself in biting sarcasm, un-necessary aggression towards peers, hard pushy selling with customers, rude and belligerent behavior with support staff. The fact is that a very simple thing can have far reaching impacts both on sales, but also your internal business relationships. As a manager what are your  options.

1. You can fire the individual- this is always an option. But it is expensive and has both immediate and long term costs.
2.  A better option in my mind is to begin working on eliminating the manifestation of these issues in the office. Perhaps a first conversation would be a direct discussion with the individual on the unacceptable behaviors. Next would be implementation of a set of tasks that would short circuit the negative behavior before it becomes destructive.
    -Ask the individual to send all email through you for 30 days. Itemize the areas where the person is exhibiting behavior that is unacceptable.
    -Build escalation mechanisms so that items are handled early before it exceeds the individuals ability to respond positively, Then as the capacity of the individual increases reduce the items that get escalated.

All of these things are entirely dependent on a willingness of the individual to work with you to get better, and a level of self awareness. For individuals who are not worth working with, or are unwilling to work with you there really is only option one.  Aristotle once is attributed as having said "We are what we repeatedly do. Excellence, then, is not an act, but a habit." In building repeatable processes that help support and mitigate individual weaknesses you build excellence in your organization in addition to being a good Karmic Manager. Which will result in less turn over, happier employees, and more sales.

Moment of Zen 
“It is not the language but the speaker that we want to understand.”  -Upanishad

P.S. If you are interested in leveraging the karmic philosophy to accelerate your career or business please check out my website http://www.karmiccoach.com , and get Karma working for you!