The phrase “ignorance is bliss” comes from the 1742 poem "Ode on a Distant Prospect of Eton College" by English poet Thomas Gray.  The full quote is “Where ignorance is bliss, 'tis folly to be wise”.  

Examples of bliss in a sentence: 

• "Lying on the beach with a good book was pure bliss." 
   
• "The couple settled into a life of domestic bliss after their wedding." 
   
• "Watching the sunset over the ocean brought a feeling of utter bliss." 
   
• "The newborn baby slept peacefully, radiating a sense of bliss." 
   
• "A warm bath with calming music is my idea of perfect bliss."