What will be will be

I’m not sure who said this originally (probably good old Shakespeare again (if in doubt blame the Bard)), but it holds true that sometimes things happen that are out of our control. Learning to accept what happens rather than become agitated and upset is a great way to prevent stress. I could site examples from my own experience, but I am sure that you could cite plenty of events that have happened in your own life that you would rather had not. Think of one particular event that you did not want to happen. Try and reflect on how you handle this and the approach you took to it. Would it have been easier to handle if you had been more accepting of events and circumstances.
If things are out of your control do not waste time and energy worrying about them. To quote a line form one of Ian Flemings James Bond books: worry is a dividend paid to disaster before it is due.