One very good way to get people upset is to tell them they look upset. No matter how an employee feels, this type of comment causes many people to instantly wonder about their smile, eyes, hair, clothes, and body language, so it's off to the bathroom for a quick check with the mirror.
Presumably your fellow employees are at least as open with you as your manager, so it is revealing that they are not giving you this type of feedback at all. This raises one question: is there something about being in the presence of your manager that is upsetting you? You may want to think a little more about your working relationship with him, along with the possibility that you may be telegraphing some dissatisfaction in this area.
If you are unable to find anything that could be triggering this reaction from your manager, it is possible that your manager is personally upset with something, and, as a result, he is more likely to think that others are upset. There is also a possibility that he is upset with something about your work, and this is his way of expressing it.
It may be helpful for you to meet with him and tell him that you are not upset with anything at work, but you are concerned that he thinks you are. The matter may end there, or he may give you a valuable piece of feedback about yourself or a piece of insight into him. Either way, this is nothing that should upset you.
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