The section in the Talmud in Masechet Gittin that discusses the destruction of the Temple for several pages, seems to have a recurring theme. Complacency and arrogance are such destructive characteristics. The Jewish people were guilty of this when they thought that they were in a good way with the Romans. They assumed that they were on such good terms that they would never be harmed. Certain individuals such as Titus attributed their own success to themselves and learned the hard way that even a tiny gnat was capable of defeating him and literally drive him mad. It is a very dangerous thing when we attribute our successes to ourselves and fail to acknowledge Hashem's blessing. Anything positive that we are able to do is all a gift from G-d. We are often reminded that our physical strength and accomplishments, our wisdom and our wealth all come from G-d. If we ever allow ourselves to think it is us alone that accomplishes, we will learn that this is not the case.