Universal Law of Luggage Expansion

Whenever one goes on a vacation of any length, the luggage can never fit the same way in the suitcase as it did as one was packing for the trip.

Me: Wow, why can't I fit my clothes in this suitcase like it fit a week ago?

Friend: It's the universal law of luggage expansion, dude!

Me: Ohh yeah, that's right. Forgot!