天真岁月不忍欺青春荒唐我不负你
[tiān zhēn suì yuè bù rĕn qī qīng chūn huāng táng wŏ bù fù nĭ]
The carefree years of youth are too precious not to cherish; even if my youth has been reckless, I have never betrayed you. It suggests a sense of loyalty and dedication through good and bad times.