Update: This post was originally titled "The Annealed Mind", but it turns out that "annealing" is not what I thought it was. What I was thinking of is actually something more like "sintering". I have replaced the words throughout the post and title.
If you want to learn something, take on a new challenge, or just refine your approach to a common challenge, it's best to wipe your slate first. Regardless of your level of knowledge and experience, intentionally bring nothing of your own to the table, so that what's already in your head doesn't drown out subtle information you're not expecting. This is a very simple description of the Zen Buddhist idea called "Beginner's Mind."
What is the opposite of Beginner's Mind? It might be tempting to reverse the analogy and think of a full slate. You bring with you a reference tome of such exhaustive completeness that you feel you barely need to look at the problem before thumbing through it to find the answer. That's certainly evocative of at least one problem with expertise.
I think another illustrative way to consider both of these states is to think of the mind as a landscape, and the wisdom of experience as being constructed on top of it. As with physical buildings, these fixtures need to be maintained: occasionally scoured clean, worn bits replaced, obsolete pieces upgraded, buildings removed, replaced, or added. If this doesn't happen the landscape will subsume the buildings. Vegetation encroaches, the soil erodes here and heaves there. Constructions slide, collapse, or are swallowed up. Over time, even if they are internally functional, on the outside one might mistake them for part of the land, rather than human construction.
This is dangerous. Imagine a mind where assumptions and knowledge and solutions are taken so much for granted that they have been sintered into the surface of the mind. The thinker no longer even recognizes that they created them. They are just there, and true. Part of the substrate.
All learning requires unlearning. But how can you dismantle an idea that no longer recognize is an idea?
Wipe your slate. Be your own mental groundskeeper. However you want to think of it: remember that your experience is just ideas. Ideas are and should be soft and temporary things that grow, and change, and are replaced.