What is the "happy" hormone?
There are no hormones that make you happy, but neurotransmitters.
Hormones are released in your blood stream via glands like the adrenal gland.
Neurotransmitters are chemicals released in your brain via your brain neurons.
Dopamine and serotonin are 2 neurotransmitters that can give you the feeling of happiness and love.
Too much of any of these can make you increasingly immune to their effects, (meaning that they do not work if you get too much) but this does not naturally occur unless your mother has a mutation while you are in her womb that bathes your brain in serotonin.