Growing up, my dad's job often required that we move: about every 2 years or so, until I left home for college, our family picked up sticks for a new home. (Such was the life of lots of families who had a parent in the oil & gas industry in the 70's and 80's.) Because of this, I've never been a person who has a problem getting rid of stuff. That's not to say that I don't amass clutter -- I do, like a pro -- but every year or so, it gets to a point where I just go on a rampage and throw things away. And I'm mercurial about it, too: I just start throwing things away with abandon, sometimes not even paying that much attention to what goes in the garbage or donation bag.
And for the record, I've never regretted getting rid of anything.
But even though I don't tend to keep things, there is one thing that I can't seem to throw away. Over the last couple of decades or so, whenever I've traveled, particularly if it's to a place where I'm enjoying myself, with friends, family, whatever, if I see a rock that I like -- something smooth, usually -- I keep it as a souvenir. I have a collection of them in a glass bowl in my guest room. Why I keep them, I can't tell you: it's not like I even label where they're from. They've made several moves over time -- internationally, some of them -- and for the life of me, I can't bring myself to get rid of them. For some reason, they really mean something to me.
It's like they're just reminders of good moments -- even if I don't always remember the details.