When it comes to acting, according to Bharat Gopy, “it happens.”
There is no other rational way to explain the process of acting. As an actor, one might be supremely confident of the fact that he/she has learned the lines, knows the movements to the last inch and the proportion and scale at which the emotions should be amplified, in relation to the the way the shot has been technically composed.
One might think everything is known, so it should be easy.
As Bharat Gopy says, that knowledge in itself might be transient.