This guy's story that he shared over on Reddit's "Today I F**ked Up' thread will leave you shook. I can only imagine what that guy is doing right now, after his devastating realization...
“This happened yesterday. So, I was lying on my bed in my room at home, reading, when I heard the front door open and my flatmate come in with a girl. He clearly didn’t think I was home, because they immediately went to his room (which shares a wall with mine). I was mildly amused by this, so I decided not to go out and ruin their fun.
“Before long, they start getting down to it and, since they didn’t think I was home, they weren’t shy about being vocal. He was grunting away, and she was moaning pretty loudly, shouting his name, etc. All this noise started to turn me on, so I started masturbating, figuring that this was better than porn because it was real-life. Eventually, the girl started moaning even louder, which I took to indicate that she was cumming, and there was some definite wall-banging as well, so it didn’t take me long to finish either. Satisfied, I went back to my book.
“After about half an hour or so, I was bored of being confined to my room, so I went out into the lounge, not really caring if I’d embarrass them; we’re all adults, we can just laugh it off.
“I walked into the lounge to find my flatmate sitting on the couch, watching TV, with his arm around my little sister.
“Christ. What have I done?”