The Dangers of False Hope

The belief that humanity makes moral progress depends upon a wilful ignorance of history. It also depends upon a wilful ignorance of oneself – a refusal to recognise the extent to which selfishness and calculation reside in the heart even of our most generous emotions, awaiting their chance. Those who invest their hopes in the moral improvement of humankind are therefore in a precarious position: at any moment the veil of illusion might be swept away, revealing the bare truth of the human condition

Either they defend themselves against this possibility with artful intellectual ploys, or they give way, in the moment of truth, to a paroxysm of disappointment and misanthropy. Both of these do violence to our nature. The first condemns us to the life of unreason; the second to the life of contempt. Human beings may not be as good as the shallow optimists pretend; but nor are they as bad as the prophets and curmudgeons have painted them.

Roger Scruton Roger Sruton

and author of The Uses of Pessimism and the Dangers of False Hope

To add further:  we overestimate the limits of what we can achieve.  As a classic case, in the book Built to Last the telling sub-title is Successful Habits of Vissionary Habits.  Ten years after book was released over half the companies had under performed: some of them badly.

We badly misplace our ability to predict into the future based on current trends.  We simply don't accept that very small changes in inputs can lead to extremely large changes in outcomes.