Does Murphy's law necessarily carry negative connotations? Because when I hear people invoking it, they mean Sod's law or “mocked by fate”: of all possible outcomes the worst will happen. At some point I believed that originally Murphy's law didn't carry negative (depressing) connotations, only meant that due to human factor the first trial of a system will be unsuccessful. But reading its Wikipedia page I'm not so sure. It would make sense coming from engineering. Compare with compiling a program code written from scratch, if it's big enough it will guaranteed not run with some stupid error due do a typo or type mismatch or missed array index or whatever. Programmers don't grieve that fate is unfair to them, because errors are supposed to happen, and Murphy's law (as I thought) is just acknowledgement of this phenomenon.

The fact that people believe in Sod's law or “mocked by fate” is just confirmation bias, BTW. When something goes wrong, it's an emotional distress, that people tend to ponder for a period of time, lose mental energy on. When something goes right, it's just expected as normal, not even reflected upon. So people tend to remember bad things better. This is related to availability heuristic: bad things are easily available, good things aren't because easily forgotten and not considered important.

“Birds always dung on my car!” cries Alice, and the image of bird feces from 2 years ago are readily available. It doesn't occur to Alice that all other times except today and that day 2 years ago birds didn't crap on her car at all. This is relevant for CBT, as confirmation bias towards negative events or features lead to various cognitive distortions, e.g. overgeneralization (birds don't always crap on your car) or mental filtering (how about all days when birds didn't crap on your car?).