It is always worth stressing one more time that the human body and mind were not literally designed by anyone — no super-intelligence was involved, with an arcane purpose of its own. Rather, the body, including the neurological system and everything dependent on it, evolved through a long period of natural selection. Insofar as the process has fine-tuned us for anything, it is not for carrying out a higher being's wishes or for pursuing our own happiness (however we understand it). It is, rather, for reproductive success in the environment in which our ancestors evolved: for being able to survive long enough, in that environment, to find one or more mates, and to pass down our genetic code to the next and succeeding generations.