I guess you are right. I am putting myself another stress limit at the moment. I want none of my sketches to take more than two hours. But this is also because I feel like not taking the whole art-thing to serious lately. There where times when I let it stress me as well but at the moment I am creating only for the pleasure, and at least lately it is more enjoyable for me not to get to deep into one piece but rather to sketch a lot of fast things. But I know it can also be a pleasure to work very hard on one piece many many hours. Both ways have their times.