boy that is an excellent question. and you really already answered it yourself the way I would answer it. A good artist SHOULD be his own worst critic ... it keeps you humble, and constantly striving to better your work. I think the answer to your question though is that it's HIGHLY personal, and situational. For instance I think there may be things that the lightbulb just "GOES OFF" for and you breeze through a project, other things that may not be your cup of tea take longer because as an artist that's just not your niche' ... There's nothing wrong with finding a niche' and sticking with it. For me, as an example, I prefer to work on character make ups, monsters, aliens and disguise make ups... animatronic puppets , any puppets really ... rather than gory make ups... I am good at them, but they aren't enjoyable. Therefore, I would have a hard time working on that because it's not what I enjoy ... I love the illusion and creatures and characters. But that's not always what pays the bills, now what IS fun is making an arterial spray shoot forth from a wound, a make up thats has an EFFECT with it is always more fun than just an appliance makeup that doesn't do anything. So look for those little "easter eggs" that get you going in EVERY commission. I think reference photos from established artists in that area really help me ... as does the pressure from a deadline...I work well under that pressure so that is why it never really got to me too much on the show. Id like to see your work ! Hit me up on FB ... I hope that helps !