The human mind entertains that certain things are true by experience and self talk.
If you get bitten by every dog you meet, you may believe all dogs are vicious and there is nothing that anyone can say to convince your subconscious otherwise.
The subconscious is like a person sitting in a dark room, cut off from everything.. except a few times a day, you pick up the phone and tell it things. These things are often self affirmations, such as "I am good/bad", "I am worthy/unworthy", etc.
Your observations are also passed to your subconscious. Critical thought is the skill of looking at everything you pass to your subconscious and inspecting it for truth.
Are all dogs vicious? No.
Your perception is shaped by that subconscious. Next time you see a dog, is it seen as vicious or not?
Better than the subconscious, is your executive thought center. If you rely on your conscious, developed mind to evaluate every situation instead of your subconscious the "fight or flight" reflex calms down. You perceive a lot more than you did before.
You make everything a choice, instead of a reflex.
In short, if you keep your mind open and filter untrue, biased or toxic thoughts, you will begin to notice more about everything. Your perception changes and you make better decisions. Perhaps you identify why a person lied to you, maybe you get better at picking the telltale signs of a lie... soon enough, you don't believe all people are liars, but you can pick the ones that do.
The less you believe, the more you learn.
Not everybody is untrustworthy, it is true that many are liars. All have a reason. Find a persons greatest desires, fears and dreams, and you will go a long way to understanding that person. N
obody lies to you for no reason.
“I am the wisest man alive, for I know one thing, and that is that I know nothing.”
― Plato, The Republic