A Midnight Indulgence Gone Wrong

I'm engaged to Sarah and work night shifts at a convenience store. It's been going well until one stormy night when she called me out of the blue, asking if I could sneak into her place while she was out for an evening run. She said something about missing me and needing some comfort. I should have guessed what would happen next but didn't. We've never done anything like that before, she's usually pretty conservative when it comes to our sex life, but in the heat of the moment, I just went with it. The second she walked into her apartment, I was drawn by a mix of lust and desire. We spent hours making love on the couch while lightning cracked outside. There wasn't a single part of my body that didn't feel electric as we explored each other's limits. It felt so good to be there with her in such an illicit manner, even if it was only because she wanted a quick fix. But then reality hit me like thunder after the storm cleared: I'm engaged, and this wasn't just any night out; it was breaking every kind of trust that we've built up. Our sex life is usually tame and loving, we never do things like this at all. Even if she's open to a bit more fun now and then, this felt way off base. Worse still, I had no intention of actually sneaking into her place; it was just supposed to be about the thrill of being there when we weren't together officially. But once Sarah said she wanted me, my brain turned off completely, and I lost myself in the moment, completely forgetting every lesson I've learned about respect and consent. It's been days since that night, and despite everything feeling fine on the surface with us, I know this isn't going away anytime soon. How can I ever explain to Sarah why I acted like that without completely destroying her trust in me? It was just an indulgence gone wrong, but now it feels so much bigger than that.