Our minds and bodies were not designed. They evolved — slowly — under conditions of relatively harshness and scarcity that to a large extent no longer exist. The human "habitat" has changed radically in the past several hundred years. One might argue that we're no longer adapted to our environment. Evolution doesn't work quickly enough for that.
I'd also suggest there was widespread physical and mental suffering in the distant past. It wasn't the Garden of Eden in prehistory.