Most stressful job I've ever had - Senior Software Engineer Target Employee Review

Within a few months of working here, I turned something in a little late and was sternly talked to by three different people. The head of our group even threatened to get HR involved! I've never had anything even remotely close to this happen to me before. I'm a very conscientious and hard working person. It's also nearly impossible to know why people do and say the things they say. For example, it's possible that I was targeted for reasons that had nothing to do with me (and by the way, every single other person on the team had something late that week). I did _not_ enjoy the politics. Subsequently we were informed we were expected to work 10 hour days everyday, and work Saturdays on-demand. Ugh!