* Une vie heureuse: This is the most common and literal translation, meaning "a happy life."
* Une vie joyeuse: This translates to "a joyful life" and emphasizes a feeling of happiness and enjoyment.
* Une vie épanouie: This translates to "a fulfilling life" and suggests a life rich with meaning and purpose.
The best choice depends on the context and the specific nuance you want to convey.