I like that quote and I can define it quite well.....
Shit is -
People who use you when times are bad and then drop you like a hot potato when times are good.
Waking up late thinking it is Sunday and then realising it is Monday.
The way you feel when you realise someone you thought was a friend is actually a complete and utter c**t.
Thinking there is a bar of chocolate in the cupboard and then finding some other bugger ate it.
Looking for something and then remembering you gave it away.
Thinking you have two bottles of wine, drinking one and then realising that you only had one.
Spending weeks working on something and then fucking it up at the last stage.
Waking up on an important day with a giant yellow and red carbuncle growing on the end of your nose.
Is realising that those around you are wasters, users and tossers and that you've let them get away with stuff you shouldn't have.
Is the dawning realisation that someone you respected never deserved that respect.
That those you thought you could rely on, and would return the help you gave them, don't give a toss.
Casting off a lace shawl and then finding you don't have enough yarn to finish the cast off.
Getting the last yoghurt out of the fridge and finding it is off.
Getting on the bus to go shopping and then finding you left the list at home.
Setting off for a run and then realising you need the loo.
Planning a day outdoors and waking up to continual rain.
Getting stuck in an unexpected traffic jam.
Is something that 'happens'.
Is needing to fart at the most inappropriate times/places.
Realising that the bill you are paying should have been paid a week ago!
Planning, due to predicted high winds, a weekend out with the kites and waking up to NO wind!
I could go on forever but I think this list gives a general idea of how I define shit.