Downfall/Rather give up
From Create Your Own Story
Well, as Shania Twain put it: It was good while it lasted, but now you're past it. You won't deny you had a good time feeling her up, but with every second you realize that your non-existing sex life caused you to grope your sister. She has been a good sport about it, but enough is enough. If you were her, you certainly wouldn't like to have your hands where they are. And given that you clearly went over the line means that you should stay clear of your sister and see that you don't let your hormones.
You release Kirsten regrettingly (it did feel good to touch a girl, regardless that she is related to you), but it is the right thing to do. You cannot preclude that you'd do something stupid if you kept on holding her. Better to be safe than sorry.
