What we normally say, if repeated, may become prayers, so they say.
Take the good wish we normally say to newly weds - "May you two be happy and prosperous till you have grandchildren". When everybody whom you have invited wishes you so, then it becomes a reality. Divorce comes soon after you have grandchildren.
It is better if you all wish: "May you be happy and prosperous forever."
This phenomenon really occurs when you are performing Haj in Mecca. Everything you say or even think will often become reality.
1. "I'm scared my slipper will be lost," you said or think just before you go into the mosque for prayers. That will be the last time you see your slippers. You should never think (hope) that something bad will happen, it will happen, believe me.
2. "After prayers, you wait here," you said to your wife. So long after the prayers your wife will still be waiting for you there and you are no where to be seen. You are asking your wife to wait, so she waits! Instead You should have said: "Ee will meet here after prayers."
3. My late biras (husband of my sister-in-law) said: "It will be good if I am buried here" as somebody told him about the empty spaces in the burial ground in Medina. True to his hope, he passed away soon after after heart failure and true enough, he was buried there.
That's why we all should always be positive in our thinking or in our saying.
These are just a few examples that I know of how what we say or what we hope will become a reality.