Bliss is a state of complete happiness or joy. Marriage is often associated with this joyous feeling: people who are married and still in love are described as living in wedded bliss.
Another common association is heaven or paradise, as in eternal bliss. Bliss is from Middle English blisse, from Old English bliss, blīths. The final -s in this Old English word is actually a suffix and the word itself is related to blīthe, the source of modern English blithe, which means happy.