Guilt after my Granny died?

My gran died over a year ago, and when she was alive, I always dreaded her visiting or having to take her out shopping with my mum (I'm 14 now). I keep thinking about how much of a botch I was and wishing I could've cared more.. Especially the last time I saw her in hospitl before she died, I wanted to rush home to read or something not important. How can I stop this guilt?