Describe a mistake you made and what you learned

The mistake that comes to mind happened about a year and a half ago, fairly early in my current job, when I sent a client the wrong version of a report — an internal draft full of blunt comments about their own data, rather than the polished version we were meant to deliver. It happened because I was rushing to get it out before a meeting and grabbed the file from the wrong folder without actually opening it to check, which in hindsight was an obviously careless thing to do. The result was about as bad as you'd expect — the client emailed my manager directly within the hour, understandably annoyed, and I spent the rest of that day fairly convinced I was about to lose the job. What I actually learned from it wasn't just 'double-check your files,' although I obviously do that religiously now; it was more about how to handle the aftermath. My manager's first question wasn't who was to blame, it was what we were going to do about it, and I ended up drafting the apology and the corrected report myself, which turned out to matter more to the client than the mistake itself had. They actually became one of our more cooperative clients afterwards, oddly enough. So the lesson that stuck wasn't really about carefulness, in the end — it was that how you respond to a mistake usually counts for more than the mistake does.