Those who suffer from an exaggerated sense of their own ability and accomplishment are continually subject to frustration, disappointment, and rage when reality intrudes and the world doesn't validate their idealized view of themselves.
Nowadays, we are confronted by a huge gap between rich and poor. This is not only morally wrong, but practically a mistake. It leads to the rich living in anxiety and the poor living in frustration, which has the potential to lead to more violence. We have to work to reduce this gap. It's truly unfair that some people should have so much while others go hungry.
Distrust brings frustration and fear. So therefore, the lonely feeling automatically come. So, lonely feeling is not creation of environment, but creation of your own mental attitude.
Unless we possess high spiritual qualifications, there is no doubt that the events life throws upon us will give rise to frustration, emotional turmoil, and other distorted states of consciousness. These imperfect states of mind in turn give rise to imperfect activities, and the seeds of suffering are ever planted in a steady flow.
In some places, there's the concept of one religion, one truth. In the Muslim world, there's the notion of Allah. The Western, multireligious modern society is some kind of a challenge to this. These, I feel, are the main causes [for terrorism], and, when combined with lots of anger and frustration, cause a huge amount of hate.
Depression seems to be related to fear, anger and frustration. When you're in a bad mood, even if you meet with your friends, you don't take pleasure in their company. But when you're in a good mood, even if things go wrong, you can cope with them without difficulty. This is why putting yourself in a good mood, making a point of developing a sense of loving kindness gives you greater inner strength.