Personal experience alone is an unreliable source for assessing the effects of an intervention
Many claims in management are solely based on the professional judgment or personal experience of managers, leaders or consultants. However, personal experience alone is not a very trustworthy source of evidence because it is highly susceptible to systematic errors and cognitive biases.
These systematic errors are the result of the way our brain is wired: we are predisposed to see order and causal relations in the world, we are over optimistic, and we process information that confirms our existing beliefs. As a result, personal experience can be biased or misleading