The stupidness of life's design

They say that stress is bad for one's health, then they come to logical conclusions as to why it causes disease.

I find this dynamic the stupidest thing I could imagine. The fact that stress can cause disease, stresses me out. I find it absurd that stress can cause disease. I smoke cigarettes, I won't quit because if smoking won't kill me, something else will. Mother nature created the circumstances, I'm just using the tools available to me to cope with my hell. 

I have always held onto a deep hatred for feeling bad. I hate the consequencial dynamics at play when misfortune strikes. How can such limits be placed on life's creations, when the pain that can happen can be limitless.