An actor is someone who portrays the character.
An actor’s job is to fully represent the character they are playing and to convince their audience that character is real by engaging them and drawing them into the story.
Effective actors do not act, they react. Actors should have honest, full inhibited emotional responses to the stimuli in the scene.
Try to immerse yourself in the scene to the point that you can just react without pretending or preplanning. Just let it happen to you because you are the character. Live the character and do what the character does. Because the real acting is about reacting.
That’s why Actors give more powerful and truthful performances when they are reacting to their external environment and to the actor.