A ‣ When things go right 
If something … | this means … |
worked like a dream | a plan succeeded absolutely perfectly |
went/ran like clockwork | it went smoothly, with no difficulties |
is up and running | it has begun to work as planned |
is falling into place | it is on the point of starting to work well |
is looking up | it is looking very positive |
B ‣ When things go wrong: reacting in conversation 
Oh no! That’s all we need/needed! [in response to news that makes current problems even worse]
That’s the last thing I wanted to hear! [in response to news that fulfils your worst fears]
This is like a bad dream! [when one bad thing after another happens in quick succession]
It’s a real nightmare / my worst nightmare. [used very generally, e.g. about traffic jams, computers going wrong]
What a pain! [used very generally, in response to any situation that causes you difficulty]
C ‣ Confusing situations or situations you don’t understand 
Her sudden question threw me completely. [I didn’t know how to respond]
The meeting was a complete shambles. [a totally disorganised and chaotic event]
It’s a mystery to me how people know about my private life. [it’s something I cannot understand]
I’m sorry, we must have got our wires crossed. I thought the meeting was at 11, not 10.30. [there must have been a miscommunication/misunderstanding]
I’m not with you. / You’ve lost me there. [what you have said has confused me]
D ‣ Happiness and sadness 

expression | meaning |
to be on top of the world / on cloud nine / over the moon | to be extremely happy |
to be in (your) element / to be made for | to be ideally suited for |
to be fed up to the back teeth | to be extremely unhappy, disappointed |
to be down in the dumps / down in the mouth | to be depressed |