Make up your mind.
"make up one' s mind ""下定決心"
eg: I just couldn' t make up my mind over what to wear to my best friend' s wedding.
我為參加我好朋友的婚禮穿什么衣服而拿不定主意.
I have to make up my mind quickly over/ about where to go for National Day.
國慶節(jié)去哪兒玩我得快點(diǎn)下頂決心.