How do you talk to yourself vs How you talk to your best friend? 

Craig L Manning, he is BYU Athletics' Mental Strength Coach. He says, “Faith begins with how you talk to yourself.”

“be your own best friend not your own worst enemy. Taking the battles inside—firing mortal shells into your very soul—is potentially one of the most damaging of all human activities.”  - Sister Patricia T Holland (correction her BYU Devo is called "Be Renewed in the Spirit of your Mind" sounds like a more sophisticated title)