My top salesperson was let go because she lacked a vital soft skill—'the red flag started waving'

Louie Bernstein fired his best salesperson because sometimes bosses have to make difficult decisions.

In 1986, a 34-year-old founded an Atlanta-based IT training company called MindIQ. Later, he hired someone who became his top salesperson, Bernstein shared in a LinkedIn video series.

Bernstein, a 72-year-old sales executive and leadership consultant, stated that he interviewed a woman who appeared great and had a good personality. He believed she was qualified and made her an offer. To his surprise, she immediately started making sales.

He discovered that she lacked coachability, which made her a nightmare to work with, once he started working with her.

"After Bernstein's departure, sales improved and the office's attitude and harmony improved."

You can't 'outsource' hard choices

Bernstein's salesperson frequently bragged about her superior performance and looked down on her colleagues, which left a sour taste in their mouths. When Bernstein discovered her behavior, he advised her to change, but she refused. Despite her impressive sales record, Bernstein chose to overlook her behavior and sweep it under the rug.

"I overlooked the harmful behaviors of my top salesperson," admitted Bernstein. "A warning sign emerged, but I chose to give her the benefit of the doubt."

Instead of handling the issue himself, Bernstein told his employees to work out their differences on their own, resulting in an explosive argument with yelling and crying, said Bernstein.

"At some point, a manager must recognize the need to make tough choices and take control, as outsourcing them is not always the solution," he stated.

Bernstein began asking job candidates questions such as "How did you collaborate with someone when you faced a problem during a project?" and "How do you handle disagreements with others?" and considering their answers carefully.

The type of employee you never want to be

In April, CNBC Make It reported that workplace culture expert Tom Gimbel stated that acting like one is owed something or above reproach and constructive criticism is a significant red flag in any workplace.

If you struggle to receive tough feedback gracefully, leadership and mental toughness expert Scott Mautz has some tips for you.

"Focus on your breath and name your emotions to gain control over them," Mautz advised in a CNBC Make It article last month.

To fully comprehend feedback, listen and inquire, advised Mautz. "Emotional management is not about suppressing feelings, but controlling them to act with purpose.

Mautz wrote that the more you can separate the ego-bruising part of the feedback from anything that could be interpreted as genuine advice meant to improve your performance, the more you'll show that you're coachable and able to incorporate feedback into your job performance.

To earn extra money online, sign up for CNBC's course on passive income streams, starting tips, and real-life success stories.

Sign up for CNBC Make It's newsletter to receive expert advice on work, money, and life.