There's a fella 'up there' sitting on a cloud taking a keen interest in what us mortals are doing.
"Look at that fella," he muses, "he thinks things are going along just fine. Boy have I got news for him!"
So at the worst possible moment there's a loud 'Kaching!' as this fella throws a handful of spanners in the works.

I know him well.

Even know his name.

It's Murphy.