Sketching : Full Cooperation Necessary

Why is it so hard to force myself to sketch when it is the single most helpful exercise for my art? If you feel like you have to twist your own arm to sit down and commit time to sketching, you are NOT alone!
I discovered last night I get so lost in sketching that I lose track of time. I am trying my hardest to look at it as a much needed escape, but it is tough to convince myself of this when I end up restricting my sleep to three hours a night and wake up early for the day j.o.b.
I've been thinking of ways to fix this, to work around the agony of the initial commitment to sketch. The best way I've found to do this, is "don't put it off." 
At the first moment of idle time, don't think about it, just grab your ipod, your sketchbook, and GO. Once you get the creative flow going, you will most likely have finished your sketch sesh before you realize that a few hours have gone by and you didn't waste time dragging your feet. Next thing you know, scheduled bedtime! VOILA!


Here is a sketch I was working on last night. I'm calling it 'Warrior' for a concept of a small oil painting I want to experiment with. You'll notice that many of my drawings, sketches especially, do not have a whole lot of line work in them. I have trouble seeing forms in lines, I interpret shadows as shapes and block everything in that way to get proper proportions. Haven't quite figured out why my brain works this way, or if I will or should "correct" this; it seems peculiar to me but it is the way my eyes have always interpreted things.