Interesting! My opinion is that there's an equilibrium in between discipline and letting your mind go. Once you trained with discipline on some techniques, you can let your mind take over and what you've learn the hard way will help you get where you want (even if you don't know or don't want to know where you go). But too much of control it and indeed you might end up with something shallow. Espcecially if there's boredom involved! I compare it a bit with driving, once you learned, it's automatic. While on the road, don't think too much and let your training operate or you get confused!
There also a lot this in electronic music, impressive display of mastered techniques with a totally boring result.
Also personnally I like to sketch a lot to not have the constrain of having something good but then when I start a project, I like to have that constrain. I actually get bored without it.
Thanks @haedre for the return :)
I never do preparation sketches... I simply can't work twice on the same thing. All enregy goes in initial creation and then into its organic progressive modifications.
That said... That could simply mean all my work is a sketching session :D