Don't fear a few closed doors — knock on enough and one will open.
Tips
usage
Almost always paired with 吃 ('to eat'): 吃闭门羹 = 'to be turned away.' The soup you 'eat' is the refusal itself.
history
From Tang-dynasty 《云仙杂记》: a Xuancheng courtesan named Shi Feng screened suitors — the ones she refused were sent away with a bowl of 'closed-door soup' instead of an audience.