Need synonyms for most lighthearted ? Here's a list of similar words  from our thesaurus  that you can use instead. 
Superlative for cheerfully unconcerned about the future or things in general
      “His books of stories, fables, songs, poems, plays, and reminiscences reflect his lighthearted  attitude to life.”
  
Superlative for happy or cheerful in mood or disposition
      “Macphail remained lighthearted  despite the negative publicity generated by the opposition press in Grey County.”
  
Superlative for enjoyable or entertaining in an agreeable or inoffensive way
      “Lighthearted  comedy, with its belittlement of everyday problems, is thought to have more of this capacity to brighten one's mood than, say, crime drama and tragedy.”