ON ACTING: Performance "Reality" Trumps Rehearsal "Choices"
During a performance, what the actor-as-character actually feels at any point must be enacted; even if that spontaneously-felt reality goes against what the actor prepared to feel in rehearsal (the actor's "choices", so to speak).
However, an excellently accomplished actor can learn to narrow the range of possible spontaneous feelings felt within the scene to feelings fairly proximate to what the actor had chosen to feel in rehearsal. It's similar to someone in real everyday life saying: "I'm going to have a good time whatever happens"...and does! Or, "I don't care what she says, it's going to anger me"...and anger ensues.
However, the good actor knows...and this is very critcal...the "good time" or the "anger", while it can be made to be experienced every time...will also always be a little (spontaneous) different ("proximate", not exact) each and every time it is acted. Reality in good acting demands nothing less.
Creating spontaneous freedom of feeling within narrow design is one of the essences of good emotional-acting craft.