I think that you forget about spirituality, it is very important for us to answer the question of what we are living for and what our purpose is of life and who we are. Are we here to just eat and sleep ? Or we have talent and capabilities that distinguishes us from animals. The bitter thing is that we see that animals eat and sleep much better than we do . And they seem more satisfied with their lives than we do . So from this point of view, we look more miserable than they. So I think it 's better to reconsider the criterion of happiness