When our attention is distracted we carry out highly practised behaviours automatically, occasionally at inappropriate times.
Like putting the milk out and the cat in the fridge.
In a classic diary study of everyday slips and lapses Reason (1979) got people to describe all sorts of cute out-of-context slips.
One person reported unwrapping a sweet (candy to the rest of you), throwing the sweet away and putting the wrapper in his mouth, another to putting shaving cream on his toothbrush and another to going upstairs to change for the evening, then finding himself wearing pyjamas.
Although practice makes perfect, it can also make an unthinking robot.
See other ways attention goes wrong at http://www.spring.org.uk/2009/04/18-ways-attention-goes-wrong.php