The Optimism Bias; Could turn into complacency, IMHO

Some time back I seem to recall reading a bit od research that seemed to indicate that people with mild depression are usually the mosat realistic.

both neuroscience and social science suggest that we are more optimistic than realistic. On average, we expect things to turn out better than they wind up being. People hugely underestimate their chances of getting divorced, losing their job or being diagnosed with cancer; expect their children to be extraordinarily gifted; envision themselves achieving more than their peers; and overestimate their likely life span

The implication of this is that the rest of us are somewhat optimistic and unrealistically so. This article explores whay actually this may be a useful thing in human beings:

To make progress, we need to be able to imagine alternative realities – better ones – and we need to believe that we can achieve them. Such faith helps motivate us to pursue our goals. Optimists in general work longer hours and tend to earn more. Economists at Duke University found that optimists even save more. And although they are not less likely to divorce, they are more likely to remarry

Now it seems to me that it's worth noting another couple of implications -at least I think they are.
One is that another facet of over-optimism is what we call complacency: if we tend to assume things will be alright, that surely means that we're not disposed to actively do something towards changing things; we'll be fine; we can afford to be complacent. Perhaps it even relates to what appears to be widespread political apathy? This is why it takes such a lot of effort to change people's behaviour to avoid potential detriments: we have to shift the dead-weight of possibly misplaced hope and complacent expectation.

The other is if not an implication, then a cross reference: the Woman in Genesis 3 and then Adam:
is what we see the serpent doing in that story? Riding the temptation on the back of a hopeful implied future: the first couple are not disposed by human nature to think that there could be disastrous consequences to following the optimistic sugesstion...

The Optimism Bias by Tali Sharot: extract | Science | The Observer