I wonder whether the co-worker is too conscientious for her own good. 

Yes, I know, conscientiousness usually pays off at work. Conscientious workers typically are careful and reliable. Their conscientious ways usually benefit other workers and the organisation. But not always. 

Conscientiousness can irk supervisors if they think an employee is making them look bad by pointing out supervisor errors or by being more honest or productive than the supervisor. 

Conscientiousness can also lead to burnout. Some employees become so psychologically invested in their work role that they work too much or care too much about their work or their employer. These individuals may be perfectionists who want to be perfect at work and to make sure everyone else is perfect. 

Striving for their own perfection leads them to anxiety and disappointment because the goal is impossible to meet day in and day out. Pushing others to perform perfectly leads to unpleasant social reactions. 

Highly conscientious individuals may be first in line for promotion. Once they rise in the organisation, they may annoy subordinates by being pedantic about how tasks must be done. 

Some individuals are so conscientious and fixed in their usually productive ways that they have problems altering their behaviour to meet a change in circumstances — such as working at home due to a pandemic or having a new boss who will never admit making a mistake. 

Conscientious workers may suffer more than others when the business takes a downturn. To them, they fail when the business does, even if they played no role in the problems.

Another problem that may go with conscientious behaviour is having little creativity. A person who is highly focused on completing every detail of every work task just right may have neither the ability nor the interest needed to innovate. 

I am not saying that conscientiousness at work is a bad thing. Think of it as a sharp knife. It can come in handy. But keep it under your conscious control and use it only if it helps you. Don’t play mumbly-peg with it. If you’ve never heard of that game, look it up — you’ll be amazed.