Summarize:

Create an open environment where issues can be discussed effectively. An open environment means that problems should be discussed, rather than dealt with passive aggressively or overly dramatically. If someone makes a small mistake, tell the person about it, but do not dwell on the situation. As a manager, it is your job to create an environment where employees can easily accept and fix their mistakes without fear of losing their jobs. If you do not create this environment, employees will continue to hide their mistakes and problems will not get fixed. This will help you to figure out what is causing your employees to feel so stressed out, without having to put anyone on the spot. When employees are allowed to give feedback anonymously, they are generally much more willing to do so. Forms of feedback can include: Suggestion and complaint boxes. Online anonymous polls. Working with a third party to meet with employees without disclosing which employee said certain things. Consider all of the factors for why a problem arose, and subsequently led to stressed employees. Perhaps a deadline was missed. Take a look at when the work was issued, how much work the assignment entailed (was the employee overburdened?), whether the work was on par with the employee's skill level, and if they employee has done similar assignments before. Taking a look at all of these factors can help you to figure out why the deadline was missed, and what is causing the stress. Perhaps the employee had never done an assignment like that, or had been sick or dealing with a family emergency at the time.
Handle mistakes calmly. Use different methods to collect feedback regarding workplace stress. Try to take an analytic approach to a problem, rather than leading with your emotions.