"Try to be a filter, not a sponge"
This is a line of dialogue from the movie Perks of Being a Wallflower. I am confused. Either it means that one shouldn't absorb the opinions of others wholly but only partially and not let all the negative words/criticisms get to you, as in to hear with one ear and purge it out from the other one, or to save only the solid (real part or positive concerns) and let the liquid (redundant non-concrete negative part) pass through, if I may put it in a self-created metaphorical sense. I saw the movie long back, so I don't remember the context in which dialogue was delivered. Which one is it?