Averaging down is a tactic that everyone needs to use at some point. Eventually you will buy a high by mistake and being able to average down your position makes it much more likely you get out in a positive.

The difficulty is that most people don't have spare fiat to continue to invest. It's sensible to only invest about 50% of what you are willing to invest so that you always have fiat spare for such a scenario but many of us don't do that (myself included)