why do we seek happiness???

Why you seek happiness? Because the urge comes from the deepest level, your
real Nature.  But because your sense-organs are having outward-going
tendencies, you seek that happiness in the outside world.  You desire an object,
you obtain it, and you get the happiness that you seek. But you have never
examined where that happiness comes from.  If you will allow your mind to
examine it in the right manner, I am sure you will find that that happiness which
you suppose you derive from sense-objects is not derived from sense objects but
is your real nature.  

I will prove to you how it is so: If happiness were intrinsic in sense object, it must
always be giving you happiness, from babyhood up till death.  But that is not your
experience….The object which gave you happiness in the childhood and when
you were a young man, ceases to give you happiness when you grow old.
Something else takes its place.  Thus you find that happiness is not intrinsic in
the sense-objects….Likewise, if happiness were in the mind, it must be possible
for you to enjoy that happiness without the help of sense-objects, but you do not
get it that way. And therefore it is not residing in the mind either.

Even when we are able to satisfy our desires, the repose we get is due to the fact
that it puts us in touch with our inner calm.  Real Happiness is our natural state--that is
why whenever we are in pain or distress, we want to get out of the pain or stress as
quickly as possible and get back to our natural state of peace and comfort. Whereas
when we are happy and peaceful, we do not want that state to ever end.  Another proof
that happiness is innate to us or lies within us is the fact that during deep sleep—devoid
of the awareness of our body, mind, senses, and external possessions—we feel deeply
peaceful and happy.

Thus, happiness that we seek from outside is our real nature, something intrinsic
to our very being.

Sri Atmanada (1973) goes on to explain it, thusly:
When you desire an object your mind is restless and continues to be restless
until you get the desired object.  When the desired object is got, mind comes to
rest for the time being and you get happiness.  Well, that happiness, as I have
already told you, is your real Nature.  It shines—or, at any rate, it is shinning
always, but it is taken note of—only when the mind comes to rest.  Therefore it is
your real nature that shines when you get a desired object.