In everyday life, our tendency is to protect ourselves from potential hurt. So if someone is behaving in a way that we feel threatened by (too open, too angry, too whatever), it’s perfectly reasonable to move away from them. Creating space is a much more innocuous way of creating a barrier than simply throwing up a defensive wall.
But in acting, the actor wants to use any of the partner’s behavior to move towards the partner and not away from. This means that if your partner is laughing a lot, laugh towards your partner. Step into that laughter. If your partner is crying, step towards that sadness. Reach out for it, participate in it: take it in. This is not to say that you should make yourself sad as well, although that may well happen. By stepping in, you accept whatever your partner gives you. By accepting it, you allow it to impact you. What your response is can be anything (that’s part of the wonderful thing of this: there is no wrong response).
Maybe part of the reason we move away from extreme or potentially “harmful” behavior is that we want to protect the other person. If my partner is crying, I don’t want to seem insensitive by getting angry about their sadness. But in our world, the response to get angry is welcome. It is what is. Disengagement is the only thing that isn’t the best option.
And if you do find yourself disengaging, fine! Be honest about that. By being honest about the disengagement, you will bring yourself back into moving toward the interaction with the partner. What is the disengagement about? What is the partner doing that is threatening? What do you think will happen if you engage? By being honest about these things and getting them out on the table, you can move beyond them, and towards a deeper connection with your partner.