Step 1: The biggest way to minimize stress is to plan ahead. When you plan your project, be absurdly detailed. Plan for the good things, and the disasters, and then leave yourself room to wiggle around the things you did not think about.
Step 2: Be ok going against almost all of that planning. A good project is essentially a large series of adjustments in planning. So when you have something scheduled and a disaster arises, look at your planned road map and draw out an alternate route. The plan keeps you organized, and gives you options when you need to be flexible.
Step 3: Stay Positive. Focus on the goal, and make it happen.When disasters arise, be the person that keeps everyone else from panicking. A disaster is nothing more than an opportunity to try something new. Keep your team encouraged, and remind them that success is still possible.