Is something not worth remembering? Does it affect brain negatively if I remember unimportant things? In other words: Is the capacity of the brain (or just too much chaotic data densed together) sometimes a significant factor for an individual's inteligence? Is something practically not worth remembering?
There are capacity limitation, especially at the working memory, that makes it impossible and inefficient to process everything we experience in the past. Our brain creates abstractions of things i.e. we do not remember every dog we have seen, but we remember the dog category. We forget unimportant details, but we maintain episodic memory for things that are important or recent.

The dysfunctional aspect of remembering everything can be demonstrated through a Hyperthymesia patient called AJ.


  Hyperthymestic abilities can have a detrimental effect on cognitive
  capacity. The constant, irrepressible stream of memories has caused
  significant disruption to AJ's life. She described her recollection as
  "non-stop, uncontrollable and totally exhausting" and as "a burden".


...


  At school, AJ was an average student, clearly unable to apply her
  exceptional memory to her studies.


...


  Deficits in executive functioning and anomalous lateralisation were
  also identified in AJ. These cognitive deficiencies are characteristic
  of frontostriatal disorders.