我怀念懵懵懂懂的小青春
[wŏ huái niàn mĕng mĕng dŏng dŏng de xiăo qīng chūn]
The phrase means 'I miss the naive little youthful days', which signifies a longing for the past innocent young age filled with fresh experiences and carefree fun, often regarded as beautiful youth memories.