Feel blue
Meaning/Usage: Feel sad
Explanation: Long time ago, blue was related to the rain. Whenever the fictional god Zeus was sad, he would make it rain (crying).
What a gloomy day. It makes me feel blue.
Whenever I feel blue, I like to listen to upbeat music.
Matt's feeling a little blue right now. Let's go cheer him up.
A:
Where is Matt these days? I haven't seen him in a while.
B:
He feels a little blue because he can't find a girlfriend.
A:
Let's go cheer him up.
Other Common Sentences
I feel a little depressed right now.
I don't know why, but I just feel sad.
Even though it's a nice day, I feel gloomy inside.