nightmare 噩梦；梦魇
This is a nightmare. An absolute nightmare.
这是个噩梦。彻头彻尾的噩梦。
Nobody knows what's going on -- it's a nightmare!
谁也不知道是怎么回事，真是糟透了！

ghost of the past 可怕的回忆
When she ran into her cheating ex boyfriend, it brought up the ghosts of the past.
当她碰见劈腿的前男友的时候，那段可怕的回忆就浮现出来了。
The ghost of the past still haunts me.
可怕的回忆仍然阴魂不散。

seared into my memory 回忆之殇；回忆中的剧痛
The tragedy of 9/11 is seared into my memory.
回忆起911事件，仍然让人感到非常痛苦。
The day my first girlfriend dumped me is seared in my memory.
初恋女友离开我的那一天，永远是我最痛苦的回忆。

excruciating 极痛苦的；极坏的；糟糕透顶的
The pain of watching my father die was excruciating.
看着父亲离去，是极度痛苦的回忆。

excruciating embarrassment of those moments 极度困窘的时刻
She groaned at the memory, suffering all over again the excruciating embarrassment of those moments.
她在回忆中呻吟，又一次饱尝那时所经历的极度困窘。
Noticing that I've had a piece of bok choi on my teeth all day is an excruciating embarrassment.
发现自己牙上有颗菜，真的是极度尴尬。