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."