A great actor advises: “Always assume the other actor’s performance is perfect.”
Isn’t that just beautiful?
Only an ignorant, immature actor blames others for the success or failure of their own performance. Who but a novice would whine to their director, “They’re not giving me enough to react to!” or “Well, if they behave like that then my character would do [something not indicated in the script].”
Comments like that reveal a denial of the actual process, as they can only come from someone who’s predetermined how they intend to play the scene. Theatre, one of the most collaborative art forms, must remain fluid and open to possibilities, particularly those which come from your fellows. This is especially true during rehearsal. You must give and you must take. Listen. React. Go with the flow. Play the scene without judging the other actor’s contribution.
You’ll be surprised at how much better it all turns out once you release your preconceptions. They were, after all, merely a handful of possibilities in an array of others.