People Have Theories
A theory is a model of how reality works, like the theory of gravity. People get attached to their favorite theories, even ones they don't formalize in writing. In fact, people might get most attached to informal, unspoken views. They mistake their assumptions about how things work for their reality. Some people die unhappily and, to them, unexpectedly because their theories missed something critical.
Maybe they viewed the world through their ethnicity, as in "I didn’t expect that guy to shoot me because he looked like someone from my tribe." Maybe they viewed the world like a game, as in "I thought I'd get another chance."
Nowadays, these assumptions get called cognitive bias. We all, as humans, are likely to recognize how aspects of an event confirm our theories. We do this more than we notice elements of the same incident that contradict our expectations. The mental habit has been called other things, too, and so has the act of unlearning biases. Unlearning has gone by labels like 'letting go of preconceptions' and 'embracing the paradigm shift.'
For long periods of time in many cultures, spiritual leaders played down the concepts of cognitive biases and unlearning. Those leaders asked people to 'endure' or to 'hold fast' to wrong worldviews. Still, the idea of unlearning has a respectable history.
Seeing Things As They Are
As soon as people lived long enough to need to unlearn things, discussions about the need must have arisen. 'Unlearning' came to be held in high regard by some people, at least.
Daoism is a tradition with a prominent focus on 'seeing things as they are.' Living in perfect harmony with the universe is the stated goal. In order to live in harmony, one needs to understand the world and accept it for what it is, not as what one wants it to be. Sometimes this view on living has made for good scientific observations. Long ago in China, Daoists became prominent scientists. Daoism always had a more mystical side to its philosophy, too, as expressed by the term 'ziran,' which means freeing oneself from obstructing biases and acting in a spontaneous, natural fashion, without effort.
Stoic philosophies were lost to western traditions for centuries after Stoicism was banned. When the religion was popular, though, it used multiple terms to address 'unlearning' concepts. The Stoics valued ataraxia, the trait of not being disturbed by the external world, and apatheia, the peace one achieves by giving up the passions of life. Stoicism also recognizes pathos, which refers to emotions resulting from mistaken judgments. Giving up mistaken judgments is a vital step in the Stoic concept of becoming an ideal person.
Buddhism promotes the practice of vipassana. The term refers to seeing things as they really are and it has its own, dedicated style of meditation. The meditation may have drifted from its term a bit and from its implied unlearning of bad assumptions (although I don't have first-hand experience with it). Nevertheless, the term vipassana reflects the importance of the 'unlearning' skill and a long tradition of honing it.
Zen Buddhism, in a slightly separate tradition, expands the 'unlearning' concept as far as 'unasking' a question. By unasking, a Zen practitioner indicates that the question, regardless of its answer, is not a productive one - the answer cannot give any useful insight.
Strategies
Some ways of letting go of cognitive biases are simple.
One way is to envision a different bias. It goes like this: if you are convinced people are stingy then, for a while, convince yourself that people are generous. Observe, inside yourself and in your worldly circumstances, how the change in your approach changes the world. If you normally think of yourself as short, regard yourself as tall. If you often think your neighbors are fussy, think of them as careful, hence their beautiful yard, fence, or mailbox. Put your different view into your actions.
The important thing is to be at least a little bit in control of your biases. Of course, envisioning a different bias in order to loosen the hold of a deeper, more ingrained one is just the mental or spiritual equivalent of warming up.
Another powerful method of re-learning is increasing your ability to focus. With practice, some people get very good at this underrated skill. Likewise, you can train yourself to observe without judgement. To start, it's as simple as questioning the part of you making those judgments and asking, perhaps, "what did I really witness?" In many professions, possessing sharp observation skills is essential. (Think of an air traffic controller or a detective without them.) In others professions, the skill goes unrecognized even though it conveys a significant benefit. (Imagine the results when nurses or doctors increase their powers of observation.)
There are essays and books on these strategies but personally I find that another good way is to relax and deliberately lose focus. Let observations occur naturally. Maybe, as you regard those observations, you'll let those slip away, too.
Any approach to improve un-learning or re-learning skills is valid to try. Because we all need to improve. The reason why 'seeing things as they are' is an esteemed practice in Daoism, Stoicism, and Buddhism is that clear outward sight and clear insight are related. And they are both a bit too rare. One of the reasons people have a hard time noticing things and understanding them, of course, is that people are attached to their theories.
