Try defining "happiness." "A state of well-being and contentment," says Merriam-Webster's dictionary, unhelpfully. It's like saying happiness is happiness.
Indefinable it may be, but we all know it when we feel it. Whatever it is, there's nothing better, and everything we do we do for its sake, in its name. We pursue it, work for it, sacrifice for it, do almost everything except enjoy it.
The truth is, writes novelist Akira Tachibana in the summer supplement of Bungei Shunju magazine, humanity is not well suited to happiness. Four hundred million years of evolution have conditioned us more for apprehensive anxiety than for happiness. This is as it should be and as it must be. Relaxed and happy, our primitive forest and savanna forebears would have fared badly against predators stronger, swifter, hungrier and more numerous than they.