We all do it! But more in a negative way.
Someone told me:
"Just go to the newspaper office and tell them about your project - and expect that they might say NO"
Go somewhere and expect a negative outcome?
Why?
If I expect the rejection, it will make it less painful?
NO WAY!
I'm going there expecting, that they say YES!
Maybe they won't. Maybe not that day. But I will expecting a YES and come again and again until they say YES.
It's also a technique used by salesmen - "ASSUME the sale".
They see a customer and assume he wants to buy the product.
That way of thinking influences the behavior of the salesmen and customer.
I assume a YES and if it is not a YES now, it will be a YES later.
It's like with the sun, I 100% assume it will rise again tomorrow.