Because it bores me witless to write it. All my best stories do. It's a purely rational matter of getting words onto screen and it's utterly uninspired and joyless. Squeeze out a paragraph or two. Go play solitaire. Flog myself to write another paragraph. Go play solitaire. Fiddle with first paragraph. Go play solitaire, check flist, check three other people's flist. You know the drill.
Look, I said to me, enough of this. Just do it. If you aren't going to just do it then you can forget the solitaire and the flist, you're going to do something you really hate doing with a passion: clean the front hallway of its winter's worth of tracked-in salt and beat and vacuum the mats and scrape bicycle wheel crud off the lino and wash and acrylic polish it afterwards. You know, the thing you've avoided doing for three whole months now? So decide.
My front hallway is of course now spotless.