既来之，则安之
jì​lái​zhī, zé'ān​zhī

accept the situation

既来之，则安之 (既來之，則安之) jì​lái​zhī, zé'ān​zhī
accept the situation
Since we are already here or in this situation, we should accept it, stay calm, and make the best of it.
settle them
Since they have come, we should make them comfortable or help them settle down (the original Confucian meaning regarding subjects or guests).

Sources
Definitions
CC-CEDICT