Suit oneself

Suit oneself

[Informal] It means, basically, "OK, do whatever you want; I don't care". It implies that the speaker made some attempt (perhaps small) to get the listener to do something; it's not generally something you say out of the blue. It's a pretty common idiom in US English.

♂ : I don't think I'll come to the party tonight.
♀ : All right, suit yourself.

 

♣ Movie The polar express (2004)

Conductor : If I were you, I would think about climbing on board.
(The boy hesitated and stepped back)
Conductor : Suit yourself.