If you are an experienced analyst, I believe, there is always something that can decrease your chances to screw up
On the other side, no matter how good of an analyst you are, there is no way to predict everything that may affect the end result.
However, you shouldn`t forget about the most important task of analysts - actually, it is a prediction of absolutely EVERYTHING that can influence the outcome of their decisions)
I absolutely agree with the fact that their task is the prediction of everything but that's the truth there are lots of unpredictable moments and the analysts can't be entirely sure of the eventual result