I can easily destroy negative thoughts in a second

What takes a second isn't demolition, it's interruption. A loop needs continuity to keep spinning, and continuity is surprisingly fragile — breakable by standing up, by the kettle, by walking to the window and looking at one specific tree.

None of that argues with the thought. It just removes the conditions the thought was growing in. Ten seconds on a different sensory channel and the whole thing has to start again from the beginning, and quite often it can't be bothered.

Which makes the second real, even though it isn't final. It will be back at some point. So will you, with another second.