To be alienated or separated from others basically means to be isolated from other group of people. For example when you are really different from others in your whole school (if you are mentally challenged or you are disable) and everyone just ignore you because they feel embarrassed to become friends with such people. They do not even think about your problem but they definitely should reflect on their own issue. In this case people choose to act like this and to leave you alone.
Other cases, for example, are when you choose to change yourself into a bad person. You start to do inappropriate and unhealthy things. You choose to be mean to all people and they just make a conclusion that you are not the one to be around with. You are listed as the one that has bad influence on others. So you choose to be separated from people around you. You have a negative outlook on everyone and you don't have any friends. This type of alienation is definitely chosen by you and only you can change this situation.
