Acting often feels forced when you are trying to produce the result of the scene instead of doing something to the other person. You play “heartbroken,” “dangerous,” or “natural” rather than pursuing a need.
Go back to the circumstances. What has just happened? What do you need from this person? What are they doing that makes it difficult? Then choose a simple action and let the emotion be a consequence of the struggle. You may also be controlling pace, gestures, or vocal colour because you are afraid the scene will not read. Release one layer at a time. Keep the objective. Stop planning the face. Let the partner interrupt the rhythm. Forced work is not proof that you lack talent. It is information that your attention may be on demonstrating the scene instead of living through its problem.