The truth is they are not thinking backward.  Although it appears like they are thinking backward, what is really happening is they are ignoring the thoughts that cause their emotions, and instead, focusing only on their emotions.  They have a massive perceptual problem; they can't see the depressing and twisted thoughts that started the problem in the first place.  How does this happen?

It's really quite simple.  When you have a negative thought, the amount of time it takes for your mind to generate a negative emotion consistent with that thought can be measured in fractions of a second - nanoseconds.  The time between the thought and the emotion is so quick that most people can't separate the thought from the emotion.  When the emotion pops into their mind, the thought that caused it disappears before they even notice it was there.

That's one reason why people have believed for years that depression was a problem with their emotions rather than a problem with the way they think.  Twisted thinking creates twisted emotions.  Unfortunately, twisted thoughts fly by at the speed of light, and people only notice the emotions left behind in their wake.  Therefore, therapists and patients focused primarily on emotions and acted as if backward thinking actually existed.

Excerpt from :

Zero Tolerance To Negative Thinking : Good-by Depression - Hello Positive Mind

David J Abbott M.D.