Someday, you will see all the things your parents have been doing is for your own good.
For one’s own good = for one’s sake = put oneself in one's shoes 為某人著想
One day 可以指未來的某一天
I will be a doctor one day.
Someone broke the window one day.
意近於the other day 前幾天
David heard from his old friend the other day.
Some other day 則是改天，搭配未來式
Cinday isn’t here. Maybe you can come some other day.
For the sake of N/V-ing 為了 =in order to =To VR
For the sake of your health, be sure to relax regular at work.