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Blissful
Positive Emotion
Use 'blissful' to express a strong sense of joy that is deep and peaceful. 
Naive Contentment
'Blissful' can imply a lack of awareness, as in 'blissful ignorance,' where someone is happy because they do not know about problems. 
Not Always Positive
While 'blissful' is positive, sometimes it can be used ironically to suggest an undesired state of happiness. 