lead up to:作为…的准备
These circumstances will lead up to war.
这些事件会导致战争。
However, as many of us know, the lead up to the Beijing Olympics has not been as peaceful as one would like.
但是，我想大家都有耳闻目睹，这次北京奥运的前奏没有我们预期的那么和平。

in retrospect: 回顾往事
In retrospect, at that time AIDS was not sufficiently on the radar of the Department of Peacekeeping Operations.
回顾过去，当时艾滋病并未得到维持和平行动部的充分注意。
In retrospect, the biggest blunders often seem inexplicable.
回首过去，我们发现，最严重的错误往往也是最不可思议的错误。

bummed out: 不高兴，烦恼
I had an argument with my boyfriend yesterday. I'm bummed out.
昨天我和男朋友吵架了，我很沮丧。
It's like an ongoing state of being totally bummed out.
它是一种持续的毫无兴致的状态。

the lesser of the two evils: 两害之较轻者
People voted for him as the lesser of two evils.
人们投票支持他只不过是两害相权取其轻罢了。