I am having an interesting experience at the moment picking takes from trio session I did almost a year ago. When I recorded this I was just about to head overseas to attend the Banff Jazz workshops and was feeling pretty dis-enchanted with "jazz," and didn't really enjoy the recording session.
My inner voice after the session was done went something like: "well that wasn't a very good session, it was good to do, but it's one that'll just live on the hard-drive." However, Ronny Ferella approached me regarding putting the music out on his new label, Downstream, so I've had occasion to revisit the music: now I actually like it!
So what this really confirms for me is that judging while playing is impossible. Objectivity is highly unlikely while 'in the moment' of music making. In this case, it seems my negative thinking at the time didn't result in totally unusable music and in some cases it may have actually (dare I say) added a certain aggression to my playing that I enjoy.
Here's the crux of my point though: abstaining from judgment while playing can help achieve a state of flow. When one gets stuck in the details—"Oh that line was no good," "Why can't I play in time?," "Why is the drummer doing that?"—it is difficult to let the music emerge through collaborative improvisation.
Douglas Hofstadter, in his books "I am a Strange Loop" (2007) and "Godel, Escher, Bach" (1979), argues that intelligent beings such as ourselves are designed to comprehend the world on a macro level—we don't think about the vitamins and proteins being carried through our blood-stream, but we do think about the concept of being fit and healthy, for example. For Hofstadter meaning—in every sense—is created and perceived at the macro levels, where the interaction between large symbols takes place, not at micro level where we 'can't see the forest for the trees.'
Being stuck in moment-to-moment 'micro', judgmental thinking while playing is the exact opposite of how humans create and perceive meaning. I need to focus on getting to the macro-level of listening when improvising.