Keep or Burn?

The one girl I actually fell for I broke up with almost two years ago. I'm finally moved back to my house after dad left and I'm cleaning the bookshelf in my room and I see a pile of letters from different people. I'm sifting through them to see what to shred/burn and what to keep and this letter from her is there. It's a sweet letter from when I was in the hospital, before I found out what she was doing with another man and before she fell out of love with me. So what do I do with it?