1. I thought “我原以为”，可以用来表示以前这么认为，而现在则不；

I thought I knew you.
我一直认为我了解你。（后来发现并不了解）

I thought it might be true.
我曾认为这可能是真的。（其实未必）

另外，I thought还可表示过去怎么看待人和事；

I thought it was dull.
我认为是乏味的。

I thought as much .
我也作如此想。

情景对话：

A: He disappointed us so much. 他令人很失望。

B: Yeah, I thought he's reliable. 是啊，我原以为他很可靠。（现在发现并非如此）

2. good reason 充足的理由

He gave a good reason for it.
他举出其正当理由。

Those are good reasons to expect pay to continue to grow, in spite of the outrage.
他们虽然愤怒，但这些是继续提薪的正当理由。

情景对话：

A: How dare you say that to me? 你敢这么跟我说话？

B: I think I have good reasons to stand for myself. 我想我有足够的理由坚持自己的立场。