1. stab sb in the back
stab sb in the back指的是在（某人）背后捅刀子（指伤害信任自己的人）。
He had been lied to and stabbed in the back by people that he thought were his friends.
2. draw the line
draw the line可不是“画一条线”，它的意思是是“绝不做”。
I swear a lot, but even I draw the line at saying certain words.
3. flatter yourself
Steve flatters himself that he's an excellent speaker.
flatter to deceive的意思是“以假象蒙人，掩人耳目”。
I suspect these statistics flatter to deceive.
She was flattered by his attention.
4. in a good mood
be in no mood for sth/to do sth意思是全然不想…／不想做…。
I was in no mood for chatting.
而be in the mood (for sth/to do sth)的意思是“有意（做／要…)”。
We could go out to eat, if you're in the mood.