Sentiment is a big part of collecting for me, and it's why I don't think I could ever be a good card dealer. I love cards with a good story - and there are many of them. Sometimes when I think of selling a card, I'll remember that I saw the player play as a kid, or he's my cousin's brother's uncle's girlfriend, or something like that.
I've slowly but surely been able to sell a lot lately to scale down/focus my collection, but it's been difficult for those reasons. I'm going to have to make some tough choices soon!