How to stay calm when you know you will be stressed

We all are not perfect. We all are going to fail now and then. We feel stressed when we know we are failing to do something. In such stressful situations, our thinking becomes cloudy. We are not our best when we are stressed. So, to avoid such stressful situations, we need to pre-mortem the things where  you look ahead and you try to figure out all the things that could go wrong, and then you try to figure out what you can do to prevent those things from happening, or to minimize the damage. For example, if you know that you are going to lose your house keys, then you should designate a place for hanging the keys around your home. If you are going overseas, you should have the soft copies of all the essential documents like passport, visa copy in your email so that you can show the documents to the staff if we forget them at home. So, the idea is that we all are not completely organized but organization is a gradual process and we should practise it in our personal as well as professional life to avoid stressful situations.