We can create our own goal though. For instance maybe we want to maximize happiness. So this means we should attack the core root of the problem. Our chemicals. We either need to find a drug like heroin that does not have tolerance and withdrawal or find a way to reset chemicals after drugging yourself or thirdly we just must find a way to be able to easily alter this chemical state. Then we will have solved all suffering issues. Right now we are just trying to treat symptoms.
What if brains aren't wired like that, and you become numb? That sounds like an aweful goal to have. Maybe a better one is to minimize misery & unhappiness (ideally, global minimization, not local)
There isn't one. We're simply the result of a bunch of lucky events and evolutionary forces.