If you tend to see the glass as half full, you may enjoy increased longevity.
Fill your glass up if it's half empty. One study found that optimistic people lived an average of 8 years longer than those who are generally pessimistic.
It is interesting to observe yourself. When, for example, you are discussing a possible outcome of a situation with someone else, do you take the view that it is not likely to come out well? Do you usually point out the pitfalls? Are you the one who says, "Yes, but, this bad thing could happen or, such and so could go wrong." ? You might think you are protecting yourself this way but, read the 1st paragraph again...
Also, notice others. Do you know anyone who almost always looks on the bright side? What do you think of them; do you think that they are unrealistic?
If you find that your usual habit is to be a 'doubting Thomas', skeptical, or expecting the worst, ---this is something you can change. When you see yourself do it, stop yourself, try reversing it in your mind. Gradually, you can develop a new habit, a healthy habit of being optimistic!
(This is the completion of a series of 3 posts on the topic. Stress Reduction http://therapiststhoughts.blogspot.com/2012/08/stress-reduction.html, Stress Reduction, 2 http://therapiststhoughts.blogspot.com/2012/08/stress-reduction-2.htmland this Stress Reduction, 3. Hope you enjoyed and found them useful)
An earlier post on the subject of stress: Stressed Out!!!