"Aahh" you think to yourself, "I should make sure to note that down so i remember to get it done for tomorrow".
Very good idea indeed that, but, hell, whilst you're making that note, why not embellish it with a drawing of a little man or some such?
"Fair enough" you think, so you start to draw, you draw his little eye, his little nose, mouth, etc, and your mind starts to wonder off a little bit. Before you know it, you've actually been drawing for some time, and you really should get to actually writing that note this was all in aid of.
So, you refocus yourself, turn your eyes back to that little piece of paper and...