In a very empiric way, it is obvious that a stressed person is less productive. However, there are also professions like firefighters or TV series directors seem to proof that theory is wrong and stress turns into their friend.
So, I can only talk about my own experience then...
My professional life started in a very ambiguous way and it is not something I am used to mention in my curriculum vitae. I started to work as an employee at the biggest bank at the time in Brazil. My shift went from 2 through 9 pm, and the stress was high. At that point, I didn't follow a meditation routine or even a spiritual life, and so I was suffering in my mind, body and emotions, going there, working like a donkey, going back to a very conflictive home and again next day all the same... Stress was very high; the main consequence was the mistakes I used to make, plus my co-worker-kind-of-boss' bad temper.
After a while, I retook my spiritual practice, and calmness took over me. Situations didn't change, on the contrary our responsibility was increasing (and my co-worker's bad temper too), but I felt much more relaxed and easy. Yes, at that point, I could not avoid the toll of the physical effort in my own body and I must admit I was often sick, but my mind at least was clear, which allowed me to change job and start a career.
My first benefit by embracing that calmness we all have inside was to strengthen my mind and in this way, to shield myself from the bad consequences coming from the environment. With stress, you are affected by all that is around you, physically, emotionally and mentally. Using meditation, at least I got to keep a strong mind and I start to help shaping the places I went to work.
It took me a few years to end the emotional and physical aspects of stress and reach a point today when I feel I am healthier than 20 years ago. And nowadays, besides meditation, my main medicine is silence and calmness.
We cannot avoid stress and its consequences without a proper moment or two when we focus ourselves in the self, in the moment and place where we are. With meditation and silence practices, gradually we can do it even though we are in the middle of very stressful situations.