Many photographers claim that they will never shoot a wedding because there is too much pressure. If you miss some of the key moments, you will never get another chance. I agree with this to an extent but at least weddings have hundreds of "moments" over the course of a day. If I miss a couple, it's usually not a big deal.
A first descent is another story though. In the video below, Lucas Gilman shows us all of the work that goes into capturing just 5-10 seconds. When it comes to something like this, there is absolutely no room for error.