Your mindset starts to change because of the repeated negative reactions you receive from different people in different situations, and before you realize, self negativity starts to creep in. So what is the outcome of all this negativity? Well, when your perception is wrong, your tendencies, your thoughts, and opinions turn towards the negative, giving rise to a constant inner restlessness and internal turmoil. — See more at:

http://www.dadabhagwan.org/spiritual-media/spiritual-articles/depression/