First of all, Buddhism is neither pessimistic nor optimistic. If anything at all, it is realistic, for it takes a realistic view of life and the world. It looks at things objectively (). It does not falsely lull you into living in a fool's paradise, nor does it frighten and agonize you with all kinds of imaginary fears and sins. It tells you exactly and objectively what you are and what the world around you is, and shows you the way to perfect freedom, peace, tranquility and happiness.
Societies would _not_ be better off if everyone were like Mr Spock, all rationality and no emotion. Instead, a balance - a teaming up of the internal rivals - is optimal for brains. ... Some balance of the emotional and rational systems is needed, and that balance may already be optimized by natural selection in human brains.
Constrained optimization is the art of compromise between conflicting objectives. This is what design is all about. To find fault with biological design - as Stephen Jay Gould regularly does - because it misses some idealized optimum is therefore gratuitous. Not knowing the objectives of the designer, Gould is in no position to say whether the designer has proposed a faulty compromise among those objectives.
We have an internal check and balance system. By design we are so filled with possibility, opportunity, with greatness that when we live small, within the bottom of our capability, we innately know we should be living greater than that, and it creates a disconnect inside that leads us to feeling empty, unhappy, maybe even depressed.