You know those letters you wrote in middle school, that traveled from hand-to-hand at the risk of being intercepted by a particularly stern teacher? I still have those. For all they went through to get to you, they're worth keeping. I feel the same way about cards. I've kept all of my birthday cards, as far back as 2003. I have a drawer full (that's not hoarding...).
This year, on the eve of my 22nd birthday, I dug through my drawer of memories and had a nice spell of nostalgia. And while digging through, I found a card from good, ol' 2009. From my favoritest Aunt of them all, the card probably went not understood by an 18-year-old me.
Reading it now, at 22, it spoke to me so much louder than it did then. The card means really means something now, and I'm happy that I kept it. And although it was given to me for my graduation, it's more importantly served as a guide to my 22-year-old self.
Maybe my aunt can help guide you too.