"So investors' fear of September and October is based less on evidence and more on what psychologists call "availability"-the human tendency to judge how likely an event is by how easily we can recall vivid examples of it. The horrific losses of October 2008 are hard to forget. The milder gains of 7% in October 2015 and 11% in October 2011 are hard to remember".
https://www.wsj.com/articles/to-every-thing-there-is-a-season-but-your-portfolio-shouldnt-turn-1537542045?mod=e2li
https://www.wsj.com/articles/to-every-thing-there-is-a-season-but-your-portfolio-shouldnt-turn-1537542045?mod=e2li