What cognitive bias prevents you from discarding stuff?
One possible explanation for the scenario you are describing is Endowment effect. 


  In psychology and behavioral economics, the endowment effect is the
  hypothesis that people ascribe more value to things merely because
  they own them.


One of the theories that explain the phenomenon is based on loss
aversion : 


  It was proposed by Kahneman and his colleagues that the
  endowment effect is, in part, due to the fact that once a person owns
  an item, forgoing it feels like a loss, and humans are loss-averse.