Quick. Answer this question. On a scale of 1-5, how good a driver are you? (1-being the highest and 5-being the lowest).
On such large scale surveys, 80% of the people believed that they were between 1-3. And that is statistically impossible. If most believes that they are average or above-average, then it really means that the one's that scored themselves "2" are "average" and the one's that rated themselves "3" are actually below-average and poor drivers.
We humans over rate ourselves, our skills, our competencies and capabilities to a large extent.
And in a related question, the same humans underestimated the time required to drive somewhere by an extensive margin. They were extraordinarily wrong. For e.g. if one had to drive 500 kms to somewhere, applying a speed of 100 kms per hour it would have taken 5 hours. But such an estimate does not leave margin for error, traffic, weather, accidents, emergencies, breaks for food/gas/restroom and when the actual time was tracked they were off my a margin. And obviously it is not possible to do that distance in say 4 hours or less as that would mean that the roads were closed off except for you to drive all the way through. Not even a convoy for a "President" or "Prime Minister" makes that pace.
In a nutshell, we rate our capabilities by an added margin and overestimating it and we predict the future mostly through underestimations. Something that needs to be kept in mind to look for tools and techniques to work with and reduce these biases (and several other biases) that are we humans have as built-in features.