Why do I react before I can stop myself?
Because a reaction can begin before the conscious explanation of it. The body registers a stimulus, predicts what it means and prepares an action. Awareness often receives the result after the process has started.
What may be happening
Repeated experience creates fast routes through perception, emotion and action. That speed is useful when danger is real. It also means that an old response can be triggered when the original danger is no longer present.
Knowing afterwards that a reaction was excessive does not prove that you freely chose it. It shows that explanation and action did not arrive at the same time.
Yat: the threshold
Yat names the threshold between stimulus and action: the instant in which a reaction becomes visible. It is not a magical pause outside cause and effect. It is the point at which a process that was automatic can begin to be recognised.
Why this matters
Recognition does not erase the pattern. It changes the conditions of the next response. What once felt completely inevitable can become observable, and what becomes observable can be met with greater responsibility.