QUOTE : The final book shows us that Snape was once ready to die to ease his own pain, but he accepted the offer of a second chance in order to protect someone else, difficult as that was guaranteed to be. When he does accept death, again, it is not for personal gain but to protect others. These convictions mean that Snape always knows why he is alive and what is important to him. The emotional connections necessary for a Patronus are not only available to those who remember receiving love. Those who choose to live to protect others create in themselves the same defensive strength.