Perception of predeterminism
Feelings of predeterminism can be defined as the sudden perspective or feeling that all events, including human actions, are established or decided in advance by prior causes.
This is an effect which can become spontaneously triggered and felt through a distinct change in thought processes. In terms of how it feels, it can be described as the assumption that ones internal narrative possesses "free will" and is therefore an independent decision-making agent becoming suppressed and revealed as entirely illusory.
The revelation is not a result of cognitive insight leading one onto a realization but occurs through a forced change in perspective. It creates the undeniable sensation that ones personal choices, physical actions, current situational perspective, and the very subject matter of their thought stream has always been completely predetermined by prior causes and are therefore outside of conscious control. Instead of being dictated by freewill, ones thoughts and decision making processes become felt to act as a vast and complex set of internally stored, instantly decided, pre-programmed, and completely autonomous mechanistic responses to perceived sensory input.