For example, suppose you have been having some trouble sleeping. You spend a lot of time worrying whether you will sleep well that night, and you tell people, "I don't know why, but I just don't sleep well." As try to go to sleep, you lie there and worry about whether you will be able to. Then, if something wakes you in the middle of the night, your first thought is, "Now I'll never get back to sleep."
Your thoughts are creating your sleep situation. The more attention and belief you give to the thought, "I don't sleep well," the more it becomes your experience.
What if you changed your story? What if, instead, every time you caught yourself thinking about your poor sleep, you changed your thought to, "I sleep peacefully and wake up refreshed?" What if, instead of talking to others about how poorly you sleep, you found other positive things to talk about? What if, as you were drifting off to sleep, you affirmed, "I sleep peacefully and awake rested and refreshed," and then paid attention to all of the positive things in that moment: you are warm, you are comfortable, your pillow supports you well, etc. Then, if something did wake you in the middle of the night, what if you restated your affirmation and again paid attention to the positives of the moment? Chances are, you would sleep better.
I speak from experience. This is what I did when I was struggling with regular insomnia. Nothing changed except the story I told myself about sleep, but the effects were profound.
Pay attention to the story you tell. With every story, you can tell it from a negative standpoint discussing what you don't want, or you can tell about it from a positive standpoint about the things that are good. Changing your point of view from positive to negative and focusing on what you want instead of what you don't want can make a world of difference.