When acting, you might feel different elements of the primary emotion at the same time. For instance, if your primary emotion is Joy, you might feel both confident and hopeful, or confident and proud. If you feel the former, it will express itself slightly differently than the latter pairing.
On the other hand, you might feel both Anger and Sadness at the same time, as Biff does in the confrontation scene at the end of Death of a Salesman. He is more closely connected to the Anger in the beginning of the scene and to Sadness at the end, but those two emotions co-exist throughout the entire scene. Your job, as an actor, is to let them both affect you, while making choices about which to let dominate when and how to make the move from Anger to Sadness.
Knowing that there are two different emotions governing opposite ends of the scene helps you to chart the space between them. You can allow for a gradual and natural change, with each successive line of dialogue helping you to move closer to your final emotion. But to really make this effective, you have to clearly understand the difference between the starting and ending primary emotions, and where they can overlap.
A third option is for both to exist throughout the scene, without the clear sort of delineation we find in the Death of a Salesman scene. For instance, you might experience Anger and Joy at the same time. Frustration and Pride, or Jealousy and Love. There are scenes where it is entirely appropriate to toggle between the two throughout the scene, as if you are flicking a light switch on and off.
Most relationships are not straightforward, grounded in one particular emotion. How many times can we fairly answer the query, “Tell me about your relationship” with, “Well, it’s complicated….”
“I love Mom, but she drives me crazy with her nitpicking.” “I love my brother, but I can’t help resenting him when Dad praises him to the skies.” “I love my boyfriend, but he doesn’t always give me what I need, and that makes me anguished, frustrated, or furious, depending on the moment you ask.”
If you’re this last woman, the same man makes you feel joy, love, grief, frustration, fury, heartbreak, worry, and fear – and sometimes, all at the same time! Human beings are perfectly capable of juggling such complexity of emotions. On stage, it’s harder, because you have to layer those things together intentionally, whereas you’ll do it naturally and instinctively in your real life. But if you want to create characters who seem like real people, this is exactly what you must do. When you create a flawed and contradictory character, you will probably create an interesting, watchable, and believable character, one who enriches the play you’ve been given.