Perception is important, as my first post said, and those who feel the sting of false perceptions the most are those with anxiety. Anxiety make the world look different.
A study on anxiety and perceptions shows how some people are associating cues from their environment with negative or positive memories. A benign sound is neutral on its own, but when it's a sound that was previously associated with the loss or gain of money, that sound made them anxious. Emotional experiences can lead to over-generalizing perceptual stimulus and altering perceptions of what is going on.
Study participants received a reward if they identified the recurrence of a tone correctly. Those with anxiety associated 3 of the 15 tones with money loss, money gain, or no consequence. Those with anxiety were more likely to falsely identify a new tone as one they had previously heard if they had previously heard tone that affected their emotional experience in a negative or positive way.
These differences between anxious people and the healthy control people where not explained by hearing of learning abilities. It really was the emotional state associated with sounds they previously heard. Anxiety isn't bad per se, but emotional events can lead to deeper anxiety, or full blown anxiety attacks.
If you want to read more about this study, it was in the Current Biology journal in March 2016.
Here are some news reports on the study at the time:
http://www.bbc.com/future/story/20160928-how-anxiety-warps-your-perception
http://www.huffingtonpost.com/entry/anxiety-perception-study_us_56d48e13e4b03260bf77a48e