Why does it kill me to listen to this?

I lost my grandmother on December 31,2006 and my elderly friend who was like another grandmother to me on July 28, 2009. My grandmother had this bear that played I hope you dance by Lee Anne Womack. At her funeral we played it one last time. All of a sudden I heard this song My wish by Rascal Flatts and now it reminds me of the woman that just died in July. Why does it kill me to listen to those songs now? Its like a knife just stabs me. But when i do listen to them it brings back all the memories we had. Afterwards it hurts, i feel like i've lost everything all over again. Why do these songs make me hurt so badly?