无忧无虑 is pronounced wúyōuwúlǜ and means “Be light of heart from care”. It is one of the words in the HSK 6 vocabulary, a level of the Hanyu Shuiping Kaoshi, China’s standardised Chinese proficiency test. Recognising a word on a page and recalling it when you need it are different skills, and only the second survives a conversation — which is why LexiTrail shows you 无忧无虑 again just before you would have forgotten it, rather than on a fixed schedule.