From a biological perspective, our goal in life is to reproduce, and keep our genes going and evolving. That's it. Hell, that is the only reason we try to stay alive; so we can reproduce.

However, humans have evolved far beyond our "base desires" as it were. We have cities and science and whatnot and are really, really intelligent. Therefore I say that, for humans, we choose our own "meaning of life" like happiness, creating world peace, leaving behind a legacy and so on. Those kind of things, and they are unique for each person.

I don't know what mine is, but it's probably a mixture of happiness, trying to help people and solve problems.