Learning how to sketch

I kept finding increasingly difficult to seat down and draw something, while a small pile of unfinished paintings is slowing developing in my room. After some reflections I decided to go back to sketching as a way to keep enjoying drawing stuff and stay away from those large, detailed drawing I tend to stick to.

Crayon on paper
about 21x21cm

Which was hitting literally any drawing project I was trying, because everything looked too complex, too long, too hard, and I was getting unhappy with my drawing skills.
So I found online this "Sketching for real" tutorial on Katherin Tyrrel's Pastels and Pencils site.
It was like a breath of fresh air. "My goodness - I thought - that's it! I need to go back to sketching, where I can draw happily again without spending 20 hours for a single picture."

The Roboraptor above is my first sketch following Katherin's instructions - a Roboraptor in pencil and crayons, done in about 30 minutes. All right, I confess that I made other 3 or 4 drawings of this toy, but the beast is trickier than it looks...

P.S.:
I need to thank also (again) Charley Parker for his Lines and Colors blog, as I read about Katherine's site from his posts.