Do you benefit from stress?

I thrive on being busy and active, but for me, there needs to be a balance between healthy, challenging activity and just giving myself the time and space to be so I don't define myself in terms of my accomplishments or failures. For me, stress is never beneficial, but then again, I distinguish between stress and a good challenge. A good, vital challenge fills me with determination, and it generally makes me feel happy. But stress is nothing but that--stressful! I think that when I feel really under the gun and frustrated and nothing's working out, I simply need to walk away from the situation for a little while. Being challenged is one thing, but being overwhelmed is quite another.