It's 9:00 do you know where your code is?
If you write code, it can keep you up at night worrying about how it's performing, where the next bug is coming from, and who's plotting to maliciously hacking it. And that's just in production. Before it even gets to that point you have to be concerned with regression errors, consistency among team members, branching, merging, and on and on. So how do you ever get to the point where you're comfortable and can sleep easy?