RAIN! Well, actually, rain does go back up, when it evaporates.
Gravity would have to be the answer.
Your age because your age goes up ,you grow older and your age don't go back again.
failure please improve my answer if im wrong
tomorrow
A mill.
Galaxy
The years never go down addition your age and the time
your age
rain
Age
Age, the New Year, and space go up but never come down.
The years never go down addition your age and the time
Vomit
age
age
your age
your age
rain
your age
A waterfall
Age.
Age
Your age.