What you want is to have a distribution. You will expect your opposition to be about as strong as it is. You will prepare for the possibility that it is stronger or weaker.
A distribution is nice but often you have to commit to a choice. In such cases you generally want to minimize your expected loss (or maximize the gain) and if the loss function is lopsided, the forecast implied by the choice can be very biased indeed.
Another month, another rationality quotes thread. The rules are: