Question

You'd better 空空空 of what you have done every day.你最好记录下每天所做的

Answer 1

You'd better 【keep a record 】 of what you have done every day.= You'd better take note of what you have done every day.

用 to write down 不行,因为You'd better后面要接动词原形,不能接动词不定式.