I've always enjoyed sketching. As an engineer I got into making my own mech designs (all of which I lost in a move). But lately, with life getting in the way I kinda fell off. Fast forward a few years and I have to say I have been inspired by my little brother to pick up the pencil again (also a little jealous of his skills). So I got a couple of sketchbooks!!
Aside from being a good way to practice sketching, I have found it is also a good release, an outlet if you will. Sometimes when I think i'm having a rough day for one reason or another, I pull out the sketch book and draw whatever is on my mind. Problems seem so much smaller when they're on paper. Try it!
I believe all anime fans should have a sketchbook. Actually let me back that up. Everyone should have a sketchbook. You don't have to be skilled, you just have to do it. Not only does it relax me, but I have gained much more appreciation for the work of artists like my brother and the makers of all my favorite shows. It actually makes you a better anime fan.
Lastly, it's just more fun to draw when you draw for yourself. I can only imagine the pressure on artists to create something that will be moving to other people. With my sketchbook, I am my only audience. No performance anxiety there :p.
With that, I say run out and get yourself a book. Sketching just makes you a better person, and no I don't think that's an exaggeration :).X