Optimistic or Pessimistic?

Sun Tzu's strategy is neither pessimistic or optimistic. Rather, it is a system for controlling investments while determining whether pessimism or optimism is warranted. A recent book called Breaking Muphy's Law (review here) looks at optimism or pessimism from a scientific viewpoint. The book considers research that harkens back to Sun Tzu's basic principles. According to the review:
"Her thesis is that when a pessimist gives up on a task, s/he is conserving resources whereas when the optimist spends time and energy pursuing a goal, s/he is consuming them. It makes sense for the optimist to use up those resources if the payback involves achievement which will ultimately see an increase in resources -- time, energy, finance, friendship, etc. However, if the payback does not come, all that expenditure has been for nothing. Optimists are high achievers because they are prepared to take the calculated risk of investing resources in order to achieve the desired goal."
In the end, Sun Tzu departs pretty radically from most "feel-good" philosophies. Most of those philosophies teach (as the review above notes): "Change Your Thoughts and Your Life Will Follow." Sun Tzu's approach reverses this thinking. If you improve your analysis and respond appropriately to dynamic situations, you will know when optimism (investing resources) and pessimism (conserving resources) are most appropriate.