Personally, the key to being reasonably adept at unexpected circumstances is to train yourself to be calm, rather being stressed or confused and if under pressure. If you can remain calm in an unexpected or volatile situation, you’re more than half way to dealing with it well.
I would take a deep breath and literally wear my thinking hat and mentally step back assessing the unexpected circumstance dispassionately as possible and further analyze, what is wrong? What is the threat? Why me? What must be done? In best order of sequence of how to come out of it, how and whom can I seek help from, or is it really necessary? These and other questions depending on evaluating the circumstances.
Again, the best is to stay calm, take a deep breath, step back while assessing. The only other thing suggested during an actual crisis is to hear your inner voice telling you something good and listen by accepting and working on the situation.
