What’s Really Going on: One of two things. The culprit may be vying with you for credit and deliberately cutting you out. “Technology makes passive-aggressive behavior easier. You can keep people out of the loop by pretending that you forgot to add them or by claiming there was something wrong with their reception,” says Katherine Crowley, M.Ed., a coauthor of Mean Girls at Work. Or it could be a simple mistake.

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How to React: Treat the situation as a simple mistake, even if your gut says it’s not. Firing off a sarcastic e-mail will only make you look unprofessional. “It also doesn’t work to confront the person with something like ‘You always do that. Clearly you have a problem with me,’” says Crowley. A passive-aggressive person will rarely admit to the behavior, so in the end you may look like the crazy one. If possible, handle the situation face-to-face. Go to your coworker and firmly say, “I’m sure it wasn’t your intention to leave me off that chain. Going forward, please remember to include me on all e-mails about the project.” Turn it into a simple business transaction.

Your Boss

Classic Scenario: You ask for a new project, and your boss hits you with “You know this requires 200 percent, and you’ve got so much on your plate! You are Supermom with those three kids! What do you think about Meg overseeing the project with you?”

What’s Really Going on: Make no mistake, your boss is implying that you can’t handle the job. Go ahead and get in touch with your anger, but use it wisely.

How to React: You don’t want to roll over. Neither do you want to yell that she’s not paying you enough to hire a full-time nanny. Instead, offer a compromise. In a calm, assertive manner, say, “I hear you have concerns, but it won’t be a problem. How about we keep in close contact, and if you have problems with my work, you can let me know. I’m always open to feedback.”

This article previously appeared on RealSimple.com.