स्वभावो नोपदेशेन शक्यते कर्तुमन्यथा ।
सुतप्तमपि पानीयं पुनर्गच्छति शीतताम् ॥

Meaning:
It is not possible to change the nature of a person by a good advice, though water is boiled, it invariably cools down.