花心未泯
[huā xīn wèi mĭn]
Translates loosely to 'Undying Heart-flower', indicating the core essence of one's character (heart represented by 'flower') hasn't diminished, aged, or been tainted—it remains vibrant, youthful, and perhaps still retains innocence and curiosity similar to the bloom of a fresh flower, no matter the passage of time.