No, I don't think that nature wants us to evolve as cool, calm and composed. How boring! Anyone who has ever felt excitement over an accomplishment, felt love for another, experienced a thrill of participating in a competitive sport, felt anger at an injustice or experienced a myriad of other feelings knows that life is not all about being calm and composed.
At a more basic level, those that are calm and composed would not survive the struggle for basic needs like food and shelter. I agree that periods of restful calm are lovely at times, but without some stress and excitement, life wouldn't be any fun at all.