My heart goes out to you. I so sorry your kitty is sick. It is always a hard decision to make when they get that sick. I have to make that decision a couple times and it is never easy. You will know the when the time comes that it is best for them to let go. Nineteen years is a long time to had a pet, so I'm sure you have lots of good memories and these memories will help you get through the hard times. The grief will get easier with time, but the memories never died. Best wishes to you.