If overthinking is so bad for us, why then do we do it? "The organization of our brain sets us up for overthinking," Nolen-Hoeksema contends. The thoughts and memories stored in our brains don't sit there in isolation; they are woven together in intricate networks of associations.
"When you are in a bad mood of some type—depressed, anxious, just altogether upset—your bad mood tends to trigger a cascade of thoughts associated with your mood. These thoughts may have nothing to do with the incident that put you into a bad mood in the first place, as when a poor job performance causes you to think about your aunt who died last year."
While this spiderweb organization of the brain greatly increases our efficiency of thinking, it also makes it easy for us to overthink. Being in a bad mood makes negative memories more accessible. It's not only easier to think of negative things when you are in a bad mood than when you are in a good mood, it's also easier to see interconnections between the bad things in your life. And the more you overthink, the easier it is to do it in the future.
