아..... 그렇구나, 감사합니다 littlething 씨 ..... ^_^

그흔한 약속 means = A Promise ( in others word it's a certain promises between the speakers in this case )

So  -- 그흔한 약속없이 나는 떠나가지만 -- means  <em>(Although I am)</em> Leaving you without a promise.

Wuahhh... this short sentence take me long enough and needed many explanations from you to got me to understand .... I think I still have a looooonggg way to go...  ('' -_-)a

Thanks for your correction, it's really gimme another point of view... ^_^

but ---(Although i am) leaving without <em>such a commonplace</em> promise--- I feel a bit unfit....

Actually what makes me not fully understand/ translating this sentence is " 그 흔한 " word , does it make sense if I changed it with " properly "..... so we can make a new sentence with a bit deeply meaning like :

              ---(although i am) leaving without a properly promise---

그 흔한 = properly,  ( 어때요? 그런가 돼요? ?