Summarize this article in one sentence.
Suppressing memories, like thought substitution, has been proven to help people forget negative memories. Your negative memories are usually linked to "triggers" that remind you of what you saw and how you felt. If you can force yourself to ignore the memory when it comes back into your head, you might be able to break these "episodic" links and let go. Cognitive scientists divide memories into two patterns: episodic and semantic. Episodic memory is experiential and subjective, while semantic memory is factual and objective. When you see something horrible online, it triggers an immediate and viscerally negative reaction, and it is linked in your episodic memory to things that remind you of what you saw. By forming new associations with these triggers, you may be able to gradually "forget" what you saw. Episodic memory is our mode of remembering specific things that we've experienced. These memories are usually tied to the emotional context of what happened. Thus, the memory of this horrible thing that you saw might be linked to triggers that continually bring back the image. Semantic memory is a more structured record of facts, meanings, ideas, and observations about our external world. Our brains tend to store this knowledge independently from our personal experience. Semantic memory does not usually include the emotional context. If you came across an especially horrific thing online, there's a good chance that the image pops up in your head from time to time. Try to catch your thoughts and turn them around. You can do this in two ways: you can "let go" of the thought by confronting it and coming to terms with it, or you can "suppress" the thought by pushing it deeper into your mind. When your mind turns to a dark place, try to consciously turn your awareness toward brighter things. You can look up or you can look down.
Try to push down the memory whenever it emerges. Understand how memory suppression works. Practice letting go.