Being Australian I often find myself at rugby games and I have found one of the hardest thing to do with a rugby ball is to hit the post. That is, of course, unless you need to get the ball through the posts. In this case it is almost like the posts create a magnetic field designed to pull in the ball. This in essence is what Murphy's Law is all about - If something bad can happen it will happen.
This doesn't happen purely to sporting stars but to musicians as well. For a guitarist the chance of breaking a string is 200% greater just before a gig then any other time. You will only ever loose your car keys when you are running late or in a hurry. The day you choose not to bring an umbrella even though the clouds are gathering is the day it will rain on you. Yet if you do bring an umbrella the clouds will disperse and you will be stuck carrying it with you for the day. This is Murphy using his law to, in my opinion, have a bit of a laugh or entertainment for himself.
Now some of you out there may think that Murphy's law can be avoided by the 5 P's (preparation prevents piss poor performance). However, can you really prepare for posts that attract footballs or having your keys disappear moments before walking out the door? I don't believe you can, I don't believe there is any form of protection against Murphy and his law, the only thing to do is accept it and learn to go with the flow. Don't be so ridged in your plans otherwise Murphy will see those plans changed.