Agreed, this guy (the one in the video below) is a little on the annoying side, and his teeth are far too white, but bare with him; he's got a point. Have you read Nobel Prize winner Daniel Kahneman's brilliant book 'Thinking Fast and Slow'? Within it, a world of insight into the workings of the human brain is there to be devoured, re-read and enjoyed once again.
To make a long story short, it explores the ways in which our brains operate on two levels: system 1 and system 2. System 1 thinking is fast, automatic, easy and unconscious. Examples? The way you drive your car without much thought, able to hold conversations with whoever sits in the passenger seat; the way your brain knows when one object appears closer than another, without having to do any measuring. System 1 takes a lot for granted, relying on past experiences to give your brain the easiest solution in the fastest time. It does not want there to be any effort involved. System 2, on the other hand, is slow, considered, questioning, rational but for the most part, takes a backseat to the dominant System 1. When System 1 runs into trouble, however, it calls on the help of System 2. An example of System 2 thinking would be trying to park your car in a tight space; it requires you to take your focus off the conversation you're having with your passenger, and place it firmly on the maneuver. Once the job is done, System 2 can go back to rest.
Most of the time this is a twofold system that works very well. That is, until it comes to negative thought patterns that become so habitual, so learned, that our System 1 automatically reinforces said negativity. It becomes too easy to think negatively, and as Kahneman will tell you, your brain always prioritises the easiest route. 'What do we already know, how can we apply it to this situation?' said everyone's brain. If you had fears in the past about a particular situation, and you're faced with something similar again, your brain scans for what it already knows and says 'hey, we didn't like this in the past, let's just run away again'. It's trying to protect you, but such a level of protection isn't always necessary.
This is incredibly interesting when it comes to our daily worries and tendencies towards negativity. Understanding these theories, explained furthermore here by ridiculously happy American man that you might want to punch (Brendon Burchard), will be your first huge step towards a more conscious, positive life. But be prepared, it takes some work, which of course, your brain won't initially like.