lit. once you've shot the arrow, there's no getting it back (idiom) / fig. once you started sth, there's no turning back / to have to finish what one started / to be determined to reach one's goals in spite of setbacks
The sea of bitterness has no bounds, turn your head to see the shore (idiom). Only Buddhist enlightenment can allow one to shed off the abyss of worldly suffering. / Repent and ye shall be saved!