Acting is reverse engineering
First you need to imagine what you want the audience to see. Then you need to figure out how to do it. Then you need to figure out what the thoughts behind it are.
Theatre is made from the outside. It is hollow. The audience makes all sorts of assumptions from the behaviour of the people on stage, just as we make assumptions in real life. From those assumptions we draw conclusions. Your job as a performer, as an actor, is to know how to manipulate those assumptions.
What you, the actor, think or feel is not important. What you make the audience feel is what matters.
You need to know what you want the audience to think and feel, and then you can work on what you need to think and feel in order to achieve that effect. To reverse engineer that effect.