Everything you do, or experience, or think is affected by the expectations you already have.
Take your arms, for example.
With both arms intact, your brain works swimmingly. It sends signals to your limbs, they move, they provide feedback, and your brain breathes a sigh of relief that the cycle is complete. When you expect your arm to move and it does, your expectations are fulfilled. All is well.
But if one arm were missing, this feedback loop doesn’t close. A variety of sensations, including pain, can follow.
In a fascinating book Phantoms in the Brain, Dr. Ramachandran explores the world of neuroscience through people who have lost a limb. Patients experienced phantom sensations in an extremity that no longer existed; some as simple as a fleeting tickle, others as irritating as an un-itchable itch and, in the worst of cases, pain.
The patient’s brain, having sent a signal to the missing limb, would expect a response. Without receiving one, its neural pathways would get confused, causing severe phantom pain where none should be possible.
Or take relationships, for example.