It's hard to forget someone who gave you so much to remember. 

Sometimes people think if they're single no one can hurt them... but being single and thinking about memories can kill you. Feelings don't die. We all keep them alive by feeding them memories. That's the exact reason why it is so hard to move on from a loved one. 

It's sad when the people who gave you the best memories, become a memory. But you have to move on, it's just a chapter in the past. Don't close the book, just turn the page.