And The Question Is...
When we ask 'Does positive thinking work?' we can take into account the fact that our thoughts do shape our attitudes, and that our attitudes define our interactions with the world.
From this perspective, maintaining a positive frame of mind can help us to deal with the events of our lives in a more relaxed and positive manner.
For instance: when I operate under the belief that all that I experience helps me to grow, I may see how any difficult circumstances contain something of value for me.
Those of us who believe in the power of positive thinking also have a certain level of trust.
A positive thinker knows that thinking positively may not create immediate changes (though in my personal experience sometimes it does), but it surely will overtime.
Therefore there is a certain level of trust or faith in the belief that our thoughts affect our reality.
A certain current of thought explains that positive thinking doesn't work for everybody.
For instance, defensive pessimists use a strategy that could look like negative thinking to optimist people, but that helps them to cope with anxiety and to be successful. This strategy is also called negative positive thinking. You can read more about it in "The positive power of negative thinking".
People who experience a large amount of distress due to serious problems, like chronic alcoholism or a history of family abuse, may find that positive thinking is not the quickest or most appropriate solution to overcome their issues, since many other factors are involved.
In these cases, positive thinking may only work if combined with other forms of therapy, like counselling, NLP or CBT.
My personal answer is Yes, positive thinking works: it makes us feel better and it helps us 'manifest' what we want to live in our physical experience.
I have experienced actively thinking in a positive way about certain aspects of my life, and obtaining my desired results - from health, to money, to particular events.
However, that is just my personal experience and you may well find someone else who defends that positive thinking does not work. You can in fact find a very good and valid critique of positive thinking in the book "Smile or die"). However, whatever belief we choose to hold about positive thinking, it is true that how we think about any issue does affect the way we experience it.
Remember that ultimately you've got the power to choose how you think about anything. My opinion is that whatever we choose to believe becomes true for us. Looping the loop, if I believe that positive thinking works for me then that will be the case ;)