Of course she's mad

"Did you...", Vanessa realized what had happened. She tried her best to compose herself but I could clearly see how angry she was. After a few more seconds of her being silent and me just being frozen in fear, she finally said something.

"What the fuck is wrong with you?!" Vanessa whispered as loud as she could, trying to stay quiet, because she didn't want any more attention. She looked at me angrily. "You can't just put your dick in someone's mouth, John!"
"I am so indredibly sorry, which I know is stupid to say and doesn't help me in this situation. It's just....my lust took over me, it was almost like I got possessed or som-"
"Just shut up!", Vanessa cut me off. "Lucky for you that I am such a nice person. I won't tell anyone. But you better not do anything like that again and when I want something from you, you better help me!"

With that she got up and left, leaving me sitting there. I was relieved that she wasn't going to tell anyone. But I still felt bad for doing it. Although it was incredible.
Why does it have to feel so good to be bad?