> Although depressed individuals are thought to have a negative cognitive bias [...] depressive realism argues not only that this negativity may reflect a more accurate appraisal of the world but also that non-depressed individuals' appraisals are positively biased.

Makes sense. Unless you have some kind of solid evidence to suggest that things will go well, there's no basis for being positive. At most you could argue that being positive can increase motivation, confidence, etc. But you have to weigh that against the risk for disappointment, discouragement, etc in the long run if you encounter repeated failure or disillusionment. And motivation aside, being realistic can be more helpful than being positive for some people.

This may actually be true, but to what point. Choosing to ignore the shitty things that are happening in your world is a pretty good survival tactic. After all there is a pretty reasonable chance that the shitty thing won't directly impact you, giving you a chance to actually improve your situation.