My mind shifts between a range of different mental processes when when playing. Sometimes I think more about foundational theory concepts. For example I might think about chord tones or the key center and scale. Other times I play by ear. This entails sort of anticipating what comes next harmonically, while simultaneously imagining and playing a line. I find that I can play about 90% of common jazz standards, but many tunes tend to have a couple of points where the changes throw me off. So unfortunately this ties me to the pages of the Real Book.
If I get lost in one process, another process may help me cover. For example if I am playing a jazz standard by ear and get to a point where I don't know what to do next, I simply look at the page and revert back to thinking about chord tones or some other foundational concept. I may play most of the A section of a tune by ear and the need to look at the music to work my way through a few changes. Then I may play through most of the B section by ear, until I need to look at the music again.
My belief is the chord symbols became archetypes. Over the years I have built up a library of automated playing processes and knowledge. When I see a chord symbol it opens up a knowledge-base so I can choose an automate response or thought process.
My ears are always part of the process. I tend to play different in response to others. So, IMHO it's important to listen to what is going on around you, even when reading notes on a page.