shí​bù​zài​lái

opportunity knocks but once

Senses

时不再来/ 時不再來 shí​bù​zài​lái (also shí​bú​zài​lái) opportunity knocks but once

Time or opportunity once lost will never come back again; often used to encourage someone to seize the moment, and frequently paired with 机不可失 jī​bù​kě​shī.

References

see 时不再来/時不再來 机不可失/機不可失