Some people, especially the ones who were brought up in an aggressive atmosphere, fear and do not accept any type of aggression both in themselves and in others. As children, they have learnt that aggression is disastrous, and they have suffered a lot due to somebody?s ? most probably one or both of their parent?s ? aggressive upbringing. They may fear consequences of their own actions and be afraid that they may be too aggressive themselves. That is why they repress all kinds of assertive feelings in themselves, because they may fear vengeance or overly aggressive response from the person they are in contact with. This may have some milder or more severe forms. This mechanism may contribute to some further consequences, for example these people may be more vulnerable to bullying.
Obviously, the list of causes of anxiety experienced in the presence of other people or when being alone may be endless. Some people are afraid of loneliness, some are afraid of being close with others, others fear particular objects or animals. Many people are afraid of being rejected, and subconsciously decide not to get close with others, which may be the reason why they cannot build satisfying relationships.