The brain changes its' neural connections every time we use it. It is constantly looking for ways to predict and short cut what it needs to do for us.
Imagine the brain’s connection between an everyday event in our life, and how we feel, is like a path through a field of grass. The more we use that path the wider and clearer it becomes. It also becomes more and more popular. i.e. as it gets wider and clearer, it gets used more.
If that path leads to an unhelpful feeling, it can activate the fight or flight response. However, we can learn how to create a new path to a useful feeling instead.
As we continue using the new helpful path, it becomes wider and clearer. Meanwhile the old unhelpful path grows over and fades away.
The helpful feeling is now the automatic response to that everyday event.