Acute Stress is good stress.

Acute stress is short lived stress. The body is able to adapt to acute stress since it is short lived and the body is able to rebuild and come back stronger.

A good example of this is weight lifting.

When you lift weights you stress the body. As long as you don't go overboard and just do enough to change the body, the next time you go back to the gym you'll be stronger, fitter, and ready to progress to the next challenge.