Have you ever had one of those days when you run your program and it does the impossible? As in, you stare at the screen and say: "No way, that's impossible. My program couldn't have done that. Couldn't be doing that." It's a funny thing for a programmer to say, when you think about it. We are logical people - or at least we are expected to use logic in our jobs. And that is flat out a most illogical statement - contradictory on the face of it. Because it wasn't impossible. Obviously. It just happened. So what's a programmer to do? Check your assumptions! You must have made an assumption that is not valid. Assumed that data was in the table that was not - or vice versa. Assumed that you saved a change to your program that you did not. Assumed that you recompiled your program, when you had not. Etc., etc. Here's an embarrassing true story from my own long, sordid history of programs doing the impossible due to my stubborn refusal...
For the last twenty years, I have managed to transform an obsession with PL/SQL into a paying job. How cool is that?