Have you ever bought a car and then all of a sudden you see the same model everywhere on the road? When I first considered setting up my own clinic many years ago, I discovered that all of a sudden there were clinics everywhere I went. There have been there all along but I did not see them until I started to focus my mind on setting up my own clinic. The outer reality has not really changed but what has changed is my inner thoughts and focuses.
Beliefs work the same way.
Once we have decided to take on a belief, most of the time unconsciously, our brain seems to re-configure itself, re-arranging the neural pathways, and we ended up turning our focus on things and events that further validate the belief. We literally attract these things into our lives.