Oil on Arches Paper
There was a time a few years ago when I was a "Daily Painter". That is, I painted one small painting every day. Such an endeavor is a great discipline and I recommend any serious painter try it for 30 days at least. It gives you much more confidence and directness in your painting and it forces you to become very efficient in your execution. This translates to larger work after the discipline has been established and you will be amazed at how quickly and efficiently you are able to produce paintings.
However, once you have attained that, it is an equally beneficial discipline to slow yourself down and create a "slow painting" once in a while. That is to say, take your time, make sure your composition works, observe your subject, look for subtleties, tackle a difficult lighting situation and focus on light values, ponder each stroke, scumble, glaze and enjoy the process. You will probably be very pleased with the result!