One of my biggest mistakes was not firing an abrasive worker as soon as I realized I had a problem.

She was a meticulous, punctual, smart, and thorough, but her venomous comments and abrasive personality poisoned the atmosphere in our factory. My mistake? I hung onto the hope that her good qualities outweighed the bad: I didn’t fire her fast enough. Here are five reasons you should dismiss poisonous personalities as soon as you recognize them:

Great employees will quit. During our exit interview with an outgoing employee whom we considered one of our best hires in years, she confided that she began putting in motion a move to another opportunity sooner than she might have because of the corrosive attitude of her co-worker. Bad employees can cost you good employees, which is a terrible tradeoff. Dismissing difficult employees will improve workplace karma and extend the tenure of productive colleagues.

Rumors will spread. Spreading tales of company setbacks — true or untrue — is a common trait of the poisonous employee. Some people believe if they divulge secrets about their organization, they’ll raise their status with co-workers. It’s the old playground conceit: “I know something you don’t know.” It’s a sorry way to try to win friends and influence. All the person achieves, I think, is to exude a vibe they don’t have faith in anybody around them, including the very people they’re striving to impress.

Skepticism will win. Poisonous personalities encourage defeatism and challenge hope. Small businesses need hard work and reality based-optimism. Every business every day, regardless of its size, has to look in the mirror and see what it has to do to improve. Believe me, at our company the safety goggles aren’t rose-colored. I know that unalloyed self-assessment is a continual necessity. But that kind of review is different from someone fostering a negativism that there is no hope and no chance for success.

Clients will feel it. Employees with bad attitudes can’t flip an on-off switch when dealing with people inside versus those outside your company. They often disappoint customers with curt attitudes and short fuses, leaving clients to wonder, “Why am I dealing with this?”

Managers will waste time. Supervisors are dragged into smoothing over disagreements between congenial employees or clients and the dark cloud employee. The supervisor has to adjudicate multiple overreaches by the problem person. Energy and time get wasted that could be put to much better use — like growing the business.

One of my biggest managing mistakes was not terminating this posionous personality as soon as I found out that she had spread sensitive information. I put too much stock in her ability to perform the job, and didn’t pay enough heed to the impact she was having on the organization. Ability and attitude should not be mutually exclusive.