Let it Go
It could be a song reference.
It could be something that would either hurt you or annoy the fuck out of you.
Someone knocked down your food.

Friend: Let it go, man.

One of your friends, doesnt like Frozen

Person: I swear one more fucking time, if i hear that song again I'll-
You: LET IT GO! LET IT GO!

Just so you know, one cannot simply Let it go.