The importance of being positive?

(written by Lawrence Krubner, however indented passages are often quotes)

I do not care if a leader is positive, I care more about whether they have an accurate assessment of reality. This would have cheered me up:

I have nothing to offer but blood, toil, tears and sweat. We have before us an ordeal of the most grievous kind. We have before us many, many long months of struggle and of suffering.

A leader who engages in happy-talk when things are going badly is one who would make me very nervous.

All I need in a leader is the belief that ultimately success of some sort is possible. Other than that, please spare me the positive attitude.