Mixing Sodium and Chlorine results in a spontaneous, irreversible reaction that produces common salt. Once this reaction has taken place, getting the original ingredients back requires tremendous effort.
Watching a horror film causes its viewer to be scared of the dark. That same person wasn’t scared of the dark before he watched the film. He also knows that the film is simply a made-up script with made-up actors and a made-up plot. Yet, knowing all this doesn’t prevent him from being a little more timid after having watched that movie. The movie has resulted in an irreversible reaction – having seen it, he cannot unsee it.
Any information that makes us feel a certain way by-passes the logical and rational centers of the brain to invoke an irreversible reaction. In an era when we are flooded with information that is meant to trigger our emotions, the only way to keep ourselves from being affected is to carefully curate the information we consume.
Once you have read that inflammatory Whatsapp forward or watched that manipulative Youtube video, its effect is already irreversible.