It's hard to relate to someone who has such wild/extreme 'mood swings'. [=someone whose mood changes very quickly]
She turned down the lights and lit a candle to create a more romantic 'mood'. [='atmosphere']
I'm sorry. I'm just not 'in the mood to talk'. [=I do not want to talk to anyone right now]
(..) If anything goes wrong, you go out after him. Yep. Okay. Let's go get our boy. There's a mood of tension and anxiety here, outside Johnson space center. As you can see, many people have gathered here... (..)2015 The Martian