That procedure which in the beginning may be just like poison but at the end is just like nectar and which awakens one to self-realization is said to be happiness in the mode of goodness.
When we understand our relationship with God then we all will be happy. It is an essential factor for establishing peace in the world.
Joy can only be experienced when we offer our love to Krishna.
Everyone is hankering for happiness because by nature we are happy : anandamayo 'bhyasat (Vedanta-sutra 1.1.12). As spirit souls we are naturally happy, blissful.