Scared to use my sketchbook....

[ChantalFournier]

I disagree with the statement that you need to start with the right inspiration. Do you think that illustrators and concept artists go for a walk and watch a movie before getting to work in the morning?
It's a sketchbook, and it's YOUR sketchbook. No one but you will look at it unless you make them look at it. You can fill it with studies, doodles, notes crap, genius stuff, we will never know. I know it's fashionable to have an online sketchbook on CA or here, and some people loook at these and think that their own sketchbook is not up to par. But 1) You are not some bigshot concept artist, no one is having any expectations about you. 2) Even big shots don't post every scribble they ever drew online for all to see 3) if you don't censor yourself (by only trying to do "good" stuff in your sketchbook,) you will learn faster 4) even bad drawings can contain good ideas that you can redraw properly later.
When you pick up your sketchbook, decide what you want to do, thumbs, concepts, studies, brainstorm, put your butt in a chair, grab and pencil and go for it. Even if in the end you toss the sketchbook to the recycling because it's full of crap, the next sketchbook will be filled with better stuff.
Also, When I get started on a sketchbook, I write the date I start, and when I'm done I write the date I'm done. That way, I can tell how long it took me to finish.