Getting a book that tells you all about depression and anxiety is the way to really understand the nature of the condition as well as how to treat it.  Anxiety and Depression 101 is that book.

The human body can only handle a limited amount of stress, beyond which, can make it hard for you to function normally. 

While it is reasonable to experience some level of stress, when it becomes chronic, it can leave you feeling anxious, depressed, and with an inability to focus on our goals.