One word: Dog. You don't have your four-legged friend following you around your apartment back in your college town. It's nice to have a roommate who listens and doesn't talk back.

Your mom looks at you disapprovingly when you come home at 3 a.m., unlike your friends at college. They are usually linking arms with you, skipping down the street at 3 a.m. 

A fridge full of something other than week old Chinese takeout leftovers, a natty, and an apple.

You see old people and babies; you kind of forgot those existed.

Sleep is actually relevant in your life again. No more 8:30 classes or early morning obligations.

Someone other than you is the boss of you. "Sorry Mom, I'll gather my dirty clothes now."

Familiar faces of your friends from different schools, seeing them reminds you that you are back in your hometown.

It's sort of relieving in a way to not see sorority girls in Lululemon and a black parka... with Starbucks in hand, at all times. People actually have diversity in the way they look. 

The line at chipotle isn't an hour long. 

It is frowned upon to be drunk at all social interactions and your fake ID will not work anywhere in hometown.  

You now have the profound feeling of homesickness, for somewhere other than your home. You're ready to go back.