I thought I could have done it 和 I thought I could do 有什么区别?知道could have done 是虚拟语气,但我觉得这2句话意思是一样的啊.

I thought I could have done it 和 I thought I could do 有什么区别?知道could have done 是虚拟语气,但我觉得这2句话意思是一样的啊.
I thought I could have done it 和 I thought I could do 有什么区别?
知道could have done 是虚拟语气,但我觉得这2句话意思是一样的啊.

I thought I could have done it 和 I thought I could do 有什么区别?知道could have done 是虚拟语气,但我觉得这2句话意思是一样的啊.
首先,could是can的过去时.
I can swim.I could swim.一个只表示现在会游泳,一个只表示过去会游泳.
I thought I could do.vs.I think I can do.
这里的can表达的是一种能力,能够.
其次,I could have done it.表达的是一种推论,对过去发生的事的否定推论.
He is so honest that he can't have stolen your money yesterday.他那么老实,不可能昨天偷你的钱.
再次,严格来说,单个的I thought I could have done it并不能表示它是一种虚拟语气,它只是表达一种推测,一种可能.因为虚拟语气表达的一定是相反的情况.I thought I could have done it只是一种推测.也可能做了,也可能没做.而如果是虚拟语气：If I had arrived earlier,I thought I could have done it.我如果早到,我就可以做做这件事了.（事实是没有早到,事情没做成）

第一个“我以为我做到了”但实际是没能做到，一般是做完某事之后才说的话
第二个“我认为我能做到”一般是在做某事之前说的话，相信自己，加油的意思

could have done 意思是本可以做却未做，带有遗憾的口气，而could只表示有能力做（其实是can，因为前面是过去式）
继续加油