Crito
The dialogue takes place in Socrates' prison cell, where he awaits execution. He is visited before dawn by his old friend Crito, who has made arrangements to smuggle Socrates out of prison to the safety of exile. Socrates seems quite willing to await his imminent execution, and so Crito presents as many arguments as he can in order to persuade Socrates to escape. On a practical level, Socrates' death will reflect badly on his friends--people will think they did nothing to try to save him. Also, Socrates should not worry about the risk or the financial cost to his friends; these they are willing to pay, and they have also arranged to find Socrates a pleasant life in exile. On a more ethical level, Crito presents two more pressing arguments: first, if he stayed, he would be aiding his enemies in wronging him unjustly, and would thus be acting unjustly himself; and second, that he would be abandoning his sons and leaving them without a father.
Memento mori
Plato's "Phaedo", where the death of Socrates is recounted, introduces the idea that the proper practice of philosophy is "about nothing else but dying and being dead". The Stoics of classical antiquity were particularly prominent in their use of this discipline, and Seneca's letters are full of injunctions to meditate on death. The Stoic Epictetus told his students that when kissing their child, brother, or friend, they should remind themselves that they are mortal, curbing their pleasure, as do "those who stand behind men in their triumphs and remind them that they are mortal"