Check out this article by Mike Boyle, some really insightful stuff here:
http://www.t-nation.com/readTopic.do?id=1475529
Stress isn't always negative.
Positive stress, negative stress are added up like absolute values, they don't (unfortunately) cancel each other out.
If your injury prone and get colds all the time that is definitely an indication of something going on. Heck but what do I know I'm only 27!