"Gratitude is the heart's memory" --- French Proverb.
Too often we can spiral into a "victims" mentality. Thinking that the world is against us when everything seems to go wrong. Maybe a string of bad luck, or a series of disappointments begin the seed of exponential growth of negative thoughts. This spiral down of attitude can become a self fulfilling prophecy unless the mental chain can be broken. Finding your way to breaking this chain is an important survival technique.
One way that has helped me has been my journal of gratitude. Started December 3, 2007 (and now in it's third volume), I list 5 things I am grateful for each day (well it has now drifted to each week - but I need to get back into the daily practice of this again). After reading Barry Schwartz's book "The Paradox of Choice", I was determined to try out his suggestion of a Gratitude journal.
Re-reading some of my entries brings a smile to my face - one of the many powerful expressions of gratitude. The power of this smile (or a mental laugh), breaks the chain of feeling down.
"Our heart's memory will set into motion an ancient spiritual law: the more we are grateful for what we have, the more will be given to us." Sir John Marks Templeton