General synonyms:
* Unburdened
* Lighthearted
* Happy-go-lucky
* Unworried
* Relaxed
* Easygoing
* Serene
* Unconcerned
More specific synonyms:
* Bohemian: suggests a carefree spirit associated with artistic expression.
* Insouciant: implies a nonchalant, unconcerned attitude.
* Blithe: emphasizes joy and lack of worry.
* Unfettered: implies freedom from restrictions or constraints.
The best synonym for you will depend on the specific context and the meaning you want to convey.