Played around 30 tennis matches against one person. I always won, he always lost. He came close to winning many times but was somehow mentally blocked due to negative momentum (not used to winning).
One day he was down and frustrated because of it, so I said:
I’d like you to know that you will never beat me. Not today. Not tomorrow. Not in 10 years. Deal with it.
At this he laughed out loud. I was expressing his innermost belief, dragging it out of his subconscious. The statement might seem cruel, but it was actually ridiculous.
The next match, he finally won. And then he also won other matches. He only needed to win once, to know it’s POSSIBLE to repeat it.
(And why did I need him to win? Because it’s not good training to always win! )