Murphy's Law...
Granny loves Murphy's Laws.  They apply everywhere!  You'll find some scattered throughout Granny's pages, but they all lead back to the original law:  If something is going to go wrong, it will.
Basic Murphy's Laws

Anything that can go wrong will go wrong.

Left to themselves, things tend to go from bad to worse.

Nothing is as easy as it looks.

Everything takes longer than you think.

If anything simply cannot go wrong, it will anyway.

If you perceive that there are four possible ways in which a procedure can go wrong, and circumvent these, then a fifth way, unprepared for, will promptly develop.

If everything seems to be going well, you have obviously overlooked something.

Whenever you set out to do something, something else must be done first.

Every solution breeds new problems.

Other Murphy's Laws
Truck deliveries that normally take one day will take five when you are waiting for the truck.
After adding two weeks to the schedule for unexpected delays, add two more for the unexpected, unexpected delays.
Murphy's Law of Copiers: The legibility of a copy is inversely proportional to its importance.
Murphy's Law of Thermodynamics: Things get worse under pressure.
Matter will be damaged in direct proportion to its value
You can never tell which way the train went by looking at the track.
Logic is a systematic method of coming to the wrong conclusion with confidence.
An expert is one who knows more and more about less and less until he knows absolutely everything about nothing.
All great discoveries are made by mistake.
Nothing ever gets built on schedule or within budget.
A meeting is an event at which the minutes are kept and the hours are lost.
The first myth of management is that it exists.
A failure will not appear till a unit has passed final inspection.
New systems generate new problems.
To err is human, but to really foul things up requires a computer.
Any given program, when running, is obsolete.
To spot the expert, pick the one who predicts the job will take the longest and cost the most.
If it's not in the computer, it doesn't exist.
If an experiment works, something has gone wrong.
When all else fails, read the instructions.
If there is a possibility of several things going wrong the one that will cause the most damage will be the one to go wrong.
Everything that goes up must come down.
Any instrument when dropped will roll into the least accessible corner.
Any simple theory will be worded in the most complicated way.
The degree of technical competence is inversely proportional to the level of management.