Left: Pentel Pocket Brush Pen sketch on blue laid paper in that journal I got from England. The full page is almost 12 inches square and this was cropped in scanning—because it just doesn't fit on my scanner!
Yes I was up at 12:37 a.m. sketching. Sometimes I eat chocolate cake late in the evening and can't sleep. If that happens I get up and sketch dogs from photos I have from the dog park.
Eventually the caffeine effects of the chocolate (and the sugar, I suppose there's that too but I've always been more immune to that) wear off and it's off to bed I go.
Often I just know that I won't be able to sleep until I sketch something.
If you feel any similar inclination then sketch something. Don't putter around tidying up the place, or ironing your clothing for the rest of the week, or alphabetizing your books by author or subject matter…
Don't avoid what it is you really want to be doing when it comes to sketching. Just sketch. Worry about the bookshelves another day.
When you have a creative impulse, nurture it. Your mind will realize you're seriously wanting more of them and pile them on.
You may have some really creative thoughts while you vacuum the rug, but that won't get you to sketching. Only sketching gets you to more sketching.