I like the Buddhist analogy of the second arrow. The first arrow is the bad thing that happens to you, usually unexpectedly. But a second arrow may follow the first one, making you suffer even more; and the pain caused by the second arrow may last much longer than that of the first.
The second arrow is your awareness of your suffering from the first arrow and your bitterness towards the fact that it has happened to you. So the second arrow is actually shot by yourself. In most cases there is not much you can do to avoid the first arrow, but the second arrow is to a large extent within your control.