The biggest mistake you can make in trying to talk convincingly is to put your highest priority on expressing your ideas and feelings. What most people really want is to be listened to, respected, and understood. The moment people see that they are being understood, they become more motivated to understand your point of view.
When two people respect each other, the ability to be vulnerable and to reveal hurt feelings can create a powerful emotional connection that is the source of real intimacy and friendship.
Can you predict the future with absolute certainty? Your answer must be no. You have two options: You can either decide to accept yourself as an imperfect human being with limited knowledge and realize that you will at times make mistakes, or you can hate yourself for it.