但惜繁花少年时
[dàn xī fán huā shăo nián shí]
'But pity the time of youthful splendor amidst abundant flowers'. This reflects nostalgia or admiration for youth - precious and fleeting, just like beautiful but short-lived blooming flowers. It hints at both appreciation and regret about the good old days, when young with unlimited energy and joy, which is gone irretrievably.