We do not know how important something is until we lose it 什么意思

I do not know how to do I do not know how to I'm sorry I do not know how to love I do not know how to face yourself and you! If I do not know how good that the翻译 You do not know me,how can i love? 谁知道 I hate you do not know how to love I do not know how it ___.（使用） I do not know I do not know I do not know that we have no I really do not know A what to do B how to do c how can i do说明理由 I do not know how to speak well ,now,also do not think so much, We do not know how important something is until we lose it 什么意思 I do not know how long the river is=I do not know of the river. I do not do very ___ in Maths.I want to do better but do not know how. I do not know when we shall leave for Nanjing.I do not know _____ _____ leave for Nanjing. When shall we meet?I do not know(合为一句) I do not know ___ ___ meet