Murphy’s Laws

[Gawdzilla Sama]

In a house with more than one floor anything needed will be on the other floor.

[onlinebiker]

Magliozzi's Law - any nut, bolt or tool dropped while working on a car will roll underneath the car to it's geometric center.

[polymath257]

Magliozzi's Law - any nut, bolt or tool dropped while working on a car will roll underneath the car to it's geometric center.

Or, if you are under the car, to a place just out of reach away from the car.

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In a house with more than one floor anything needed will be on the other floor.

If you live in a multi-story building, you will have to visit every floor to get ready to leave...some of them twice.

[BrianSoddingBoru4]

The availability of a repair part is inversely proportional to the urgency of the need for that part. The cost of the part varies as the square of the need for it.

Boru

[Anomalocaris]

We all know the standard one: Anything which can go wrong, WILL go wrong. 

What others have you run across or made up on you own? My personal favourites are the Thee Laws Of Infernal Dynamics:

1. An object at rest will always be in the wrong place.
2. An object in motion will always be headed in the wrong direction.
3. The amount of energy required to change either of the states will always be more than you wish to expend, but never so much as to make the project impractical.

Boru

Corollary:  anything that can not go wrong, WILL go wrong.

[Gawdzilla Sama]

Go ahead and say "There's nothing to worry about" out loud, I dare you!

[Anomalocaris]

Go ahead and say "There's nothing to worry about" out loud, I dare you!

There is nothing about which worry will do any good,  except you are biologically impelled to worry about everything anyway.

[zebo-the-fat]

All machines have a "critical need sensor" the more urgent the job the higher the chance of a breakdown

[Anomalocaris]

All machines have a "critical need sensor" the more urgent the job the higher the chance of a breakdown

More sophisticated machines have a “unspeakable frustration predictor”, more frustrated you will be with a malfunction, the higher the chance of that malfunction.

[polymath257]

A crucial piece of equipment will demonstrate how crucial it is by failing when you need it most.

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Any software upgrade will reset all of your settings. It will take until the next upgrade to get them right again.