Extremely good point, Genghis.
I have a vaguely related preflight check story that I was thinking of starting a thread about, but I think it's more relevant to post it here. I was instructing - or supposed to be - last Sunday morning. I arrived at the airfield, opened up the school, went to preflight the helicopter. I was tired, had a long week, a bit fed up at working when almost no-one else seemed to be. I did the preflight on semi-automatic, as it were - after all, I'd preflighted that particular helicopter almost every day that week, and I'd been the last person to fly it. Then I stopped. I'd been round everything, but had I REALLY looked at it...was I really wide awake enough to? I went round again, and found that one of the teletemps which are on many of the crucial parts of the helicopter had started to turn black, ie something was getting hotter than it should. I wasn't sure if it was something to worry about, but I phoned the CFI, and we grounded the helicopter. A few days later the part was replaced; the engineer wasn't sure if anything was wrong with it either, but he figured replacing it was safer than not. And one or two people have complimented me on spotting it...but I very nearly didn't!
So the connection with Genghis' story? Never mind how you feel. It doesn't matter what's going on in your head, in your life, with other people and so on. You need to calm down and be alert and do your preflight checks properly....and however you feel, you can do that.