I am going to say this again, managing stress and smoking have nothing to do with each other except that stress causes rapid nicotine removal from the brain by urine acidification. Alcohol also has the same effect; you drink alcohol your urine becomes acidic the body takes the nicotine from your body and throws it to the urine to alkalize it. Quick rapid depletion of nicotine occurs the smoker enters in a withdrawal situation, smokers they need to smoke to replace the lost nicotine and at the same time assume that smokers are managing and dealing with stress. In reality, the smokers satisfy their addiction and getting their fix.
I used to have that fear too that after quitting smoking I would not be able to control my temper or my nerves or my stress because deep in my mind I thought that it was helping me. After several quit smoking attempts and living and experiencing the withdrawal symptoms, I believed that those bad feelings and unpleasant situations would carry on for the rest of my life.
The reality is that they will go away you might have some rough time the first three days, I repeat you might, and then you will see that everything that you were afraid was not real they are not real it is in your head. Once the nicotine is out of your system, then you need to retrain your brain to live without a cig and face every social situation you had as a smoker without a cig.
It is a learning procedure nobody can show you exactly how to do it, but you can make it if you make a commitment never to put another cigarette in your mouth.