Emotionally manipulative people can be difficult to deal with, particularly in the workplace, where their behavior can damage your career or sabotage team efforts. Sometimes it can be difficult to know whether a particular behavior is deliberately manipulative, but strategies for dealing with emotional manipulation don't require you to determine that.
If you have a feeling of guilt because of something a friend or co-worker said to you, it can be almost impossible to decide whether the behavior was a deliberate guilt trip. Most people try to give others the benefit of the doubt, and a deliberately manipulative person can often use this to exploit or bully others.
However, we all can say or do something that could be interpreted as emotionally manipulative, without meaning to mistreat anyone. The first step in dealing with an emotionally manipulative person is to deal with the behavior, without trying to analyze the intention behind it. You can never know another person's true intention.
Those who deliberately try to manipulate people are concerned only with the ability to gain power over others. They aren't concerned with finding a solution that benefits everyone. Negotiating with people who think this way is never going to work, since they always negotiate in bad faith. You can't be sure whether you're dealing with a person like that because you can't know what another person is really thinking.
Emotional manipulation works through indirection, so you can refuse to engage with it by not responding to indirect communication. For example, if a co-worker tells you "everyone" in the office is saying something, ask her whom she is referring to and what she thinks about the situation. You can refuse to offer your own opinion except in response to a direct question.
One common emotional manipulation tactic is to present a false choice between two alternatives, neither of which is an option you would choose on your own. When you're confronted by this kind of false choice, you can refuse to choose either option. When someone says something that makes you feel guilty, you can say "I'm sorry you feel bad," and make the same decision you would otherwise have made.
Rather than confronting an emotionally manipulative person and accusing him of trying to manipulate you, it is more effective to ignore the behavior and refuse to let it affect your own decisions. Because you can't know if another person's actions are intentional or to what degree, you should decide not to judge him, not to be angry and not to be manipulated. By refusing to engage with the manipulative behavior, you defuse it of all its power. By choosing not to judge or confront the manipulator, you can avoid becoming manipulative yourself.