曾经太过年轻心纯真透明
[céng jīng tài guò nián qīng xīn chún zhēn tòu míng]
This username expresses the reminiscence of youthful days when one's heart was innocent and transparent. The person might be looking back at their pure past with nostalgia, believing they had a sincere, straightforward attitude and emotions during those times that are irreplaceable by later experiences.