Nothing is permanent. Our relationships, the things we own, the way we feel - none of that lasts forever.
After coming home from four years of college, I threw out a lot of things that I had bought or held onto during high school and I remember how I used to think that I would have these things forever. I liked buying things because I liked how permanent they felt, sitting in my room or in my closet. What I didn't know in high school was that how I felt about all of these things would change significantly.
My old clothes, jewelry, and little doodads - I let them all go.
Even stuff isn't permanent, let alone our relationships, friendships, and feelings. Nothing good is guaranteed forever, but then again nothing bad is either.
(It's also nice to think that my current state of not yet employed - missing my college friends - and generally kind of sad/overwhelmed - isn't permanent) :)