When I started out in photography I used to think very hard about my assignments. I used to look at photographs of similar subjects and prepare mentally for a preconceived idea.
I soon learnt that this just does not work in the real world. I have learnt (and am still learning) that one needs to be flexible and prepared. Be prepared for anything to happen and adapt, a little bit like everything else in life.
I went to this particular event for the fire walking but found that the preparation was far more interesting visually. As the editor said of a picture of a man walking on coals: 'Do you have one with sparks flying or coals burning?'