Moaned this person twice knocked back life advice (5,4)
I believe the answer is:
carpe diem
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for carpe diem that I've seen before include "Gather ye rosebuds" , "make the most of today" , "Seize occasion" , "Make the most of the time you have" , "'Seize the day'" .)