Drinking fails to give satisfaction and taste; shirt front wet. Mouth not open while drinking 
Glass being applied to wrong part of face.
Buy another pint and practice in front of mirror. Continue with as many pints as necessary until drinking technique is perfect.
Drinking fails to give satisfaction and taste; beer unusually pale and clear. Glass empty. Find someone who will buy you another pint.
Feet cold and wet. Glass being held at incorrect angle. Turn glass the other way up so that the open end is pointing towards the ceiling.
Feet warm and wet.
Loss of self control.
Go and stand next to the nearest dog - after a while complain to its owner about its lack of house training and demand a pint in compensation.
Bar blurred. You are looking through the bottom of your glass. Find someone who will buy you another pint.
Bar swaying. Air turbulence unusually high - maybe due to darts match in progress. Insert a broom handle down back of jacket.
Bar moving. You are being carried out. Find out if you are being taken to another pub - if not, complain loudly that you are being hi-jacked.
You notice that the wall opposite is covered with ceiling tiles, and has a fluorescent light strip across it. You have fallen over backwards. If glass is still full and no one is standing on your drinking arm, stay put. If not, get someone to help you up and lash yourself to the bar.
Everything has gone dim and you have a mouthful of dog-ends and teeth. You have fallen over forwards. As for falling over backwards.
You have woken up to find your bed hard, cold and wet. You cannot see your bedroom walls or ceiling. You have spent the night in the gutter. Check your watch to see if it is opening time - if not, treat yourself to a lie-in.
Everything has gone dark. The pub is closing. Panic!!