The subject of each sketch was left up to me, with a suggestion that most of them should be made by observing things around us, but imaginary scenes or characters were allowed too. The instructor promised that my sketching would improve rapidly if I would spend a few minutes thinking what I had learnt from doing each sketch and apply it to the next sketch.
It was tough. Finding even a few minutes with something interesting in front of me and the right place and mood to sketch was surprisingly hard. Day by day I went from being very pleased at how my rusty, and never very good, skills were returning and utter despair that I could ever make anything worthwhile. I enjoyed the process of sketching, because it makes you stop and look, even at the very familiar and at unexpected moments (like a few minutes sitting in the car, waiting for someone).I have to admit I did not fulfil the challenge, but I did learn a great deal and more importantly, I now think that I can sketch and draw well enough to use the skill, that it is a relaxed and pleasant thing to do, and that you see much more in things if you try to capture them with (real or virtual) pencil and paper.
Like all these things, everything you learn (e.g. making a cleanish line) opens up the need to learn much more (e.g. how to use perspective). For that reason, I will, definitely, commit to another 30-day sketching challenge soon, and learn some more.