I see a silhouette...

A good exercise that I enjoy doing is drawing with constraints or a set of rules. Trying to be very steady, precise or obsessing over a tiny line can be a little too much sometimes so it's nice to let go and just see where the drawing is taking you.
For example, you can draw far from an easel holding the pen vertically by its end, or draw with your eyes closed, without looking at the paper, without lifting your pen... the possibilities are endless.

As an example, the next drawing was done at the V&A where I took part in a fashion illustration course a few weeks ago...

The rules were: draw the silhouette in 30sc, then focus on the creases & clothing without actually looking at the paper. And 30sc later it was time to draw the face. Not too many details, and as before, no peaking, eyes away from the paper! Boom, 30sc DONE.
I really like the superimposition effect... now of course the scale is absolutely off. I felt a bit lost, to say the least, with no space guides whatsoever. But it's a good surprise nevertheless.

On this note, I recommend the book "Drawing projects, an exploration of the language of drawing" by Mick Maslen & Jack Southern (black dog publishing). It's full of, well, drawing projects, plus tips, artists' interviews and so on. Great source of inspiration.