Is there any thing that could have turned you in to a hoarder of that thing?

Boxes, man. It used to tear me up to throw a perfectly good box in the trash. For a long time I broke them down and stored them, but ran out of room even for that.
Also, jars and plastic coffee containers. They all seemed like such Useful Things that throwing them away felt like a dreadful waste. But who has room for 30 years worth of jars and coffee cans and boxes?
But now I recycle so I sleep much easier at night. ;)