On the body level, pleasure is opposed by pain; on the mind level, happiness is opposed by unhappiness; on the soul level, joy is opposed by misery. But on the fourth, Turiya (deep sleep with awareness - Samadhi), bliss is not opposed by anything; bliss has no polar opposite to it.
Its that inner silence which is beyond pleasure and pain, beyond happiness and unhappiness, beyond joy and misery, beyond all polarities and yet it penetrates through all the states.
Bliss is natural. Bliss is the very nature of the way things are.