In for a penny, in for a pounding

[Magaret]

A sexualized version of in for a penny, in for a pound. Means almost the same thing as the original saying but in a sexual context as aforementioned. In context, it references sex with or without protection (in this case, without), and since it was done before might as well [double down] and do it again regardless of the consequences.
This was used in [Team Four Stars], Dragon Ball Z [Abridged]: Episode 60 Epilogue.