thats a long life dude. you should be stoked that you had her around for so long.
we had to put my golden retriever down a couple summers ago at age 9 since she was having really bad heart problems. so shitty. she was getting progressively worse, to the point where medication couldn't control seizures she had been having and she was having a really really bad seizure pretty much every day. after the last one, she was hurting so bad she couldn't even move. she laid on the floor for hours, unable to conjure the energy to even wag her tail, and i just laid on the floor with her, teary-eyed just patting her. we just kind of looked at each other and i could see that she was suffering. shortly thereafter, the fam took her to the vet and that was that. sad times man, but life goes on. just try not to think about times without her, think about the happy times you had with her..