When the moment of truth arrives (a negotiation, a talk, a difficult conversation), thinking about the outcome fills you with worry and tells you nothing about what to do. Winning or losing depends partly on other people; how well you carry out an action is far more up to you.
That’s why it pays to prepare with concrete instructions, three at most, that describe what you’re going to do rather than what you want to achieve. Before a negotiation, for example: listen before you respond, find out what matters to the other side, and only give something away when you get something in return. Then rehearse it in your head: recall three times you did it well, and picture how you’ll handle the difficult moments. The brain also learns by imagining, so this rehearsal adds to real practice, even though it can’t stand in for it.
It won’t guarantee the result. What it changes is what you walk in with: a useful mental plan instead of a list of everything that could go wrong. And like any training, it works through repetition: a few minutes, several times a week.