Can't wait to get it, hate it when you have it, miss it when it's gone??

This is a riddle that our 8th grade american history teacher gave for extra points... does anyone have any idea?

Money?

I'm changing my answer to Time. And that would make more sense coming from a history teacher.

The present?

Back to school
U are bored in the summer so you want to go to school
When your at school you can't wait to get out
When your out you wish to go back