Kept going for each terrible day (10)
I believe the answer is:
persevered
'kept going' is the definition.
(I've seen this before)
'each terrible day' is the wordplay.
'each' becomes 'per' ('per' can mean for each).
'terrible' becomes 'severe' (synonyms).
'day' becomes 'd' (abbreviation for day).
'per'+'severe'+'d'='PERSEVERED'
'for' acts as a link.
(Other definitions for persevered that I've seen before include "didn't give up" , "Was not deterred" , "Kept going" .)