You can't get sentimental over everything that comes in your house or there'll be no room left! My philosophy is "one thing in, one thing out." So if I buy a new shirt, I get rid of an old shirt. I try to apply the same philosophy to cards, holiday decorations, etc. So if there's one card I want to keep for some reason (I got a REALLY beautiful photo card of my new nephew this year for example), then I make sure I get rid of one other thing I was holding onto that I no longer need.
I still have too much useless junk around the house, but I'm not adding to it anymore.
This philosophy now works for me too. I seriously consider new purchases: do I need it?/ do I have a place for it? vs. is it just a whim/ dust collector?
And when I bring in something new (clothes especially), I get rid of one or more.
Watching "hoarders" made me realize that a mess can gradually take over and I never want that.
Enjoy the cards but clean out now unless there is a special photo card or christmas letter you want for later. (that's my vote