Wow a 5 year old dog! That is sad. I remember when my first bulldog came down with cancer at age 5 nearly 6.we got her to li o along u til agr 7 with surgeries, chemo, etc. i wouldnt do that again, bit 5 is so young!
As for the pain of losing them, .i can handle that. What I absolutely HATE is that period where you are trying to figure out if it is time to euthanize them or not. I now look at the eithanasia decision as a curve, and I ask the vet if our pet is in the decision curse if euthanasia is appropriate. I absolutely will not wait until the end of the curve, but I no longer mind doing it at the beginning of the curve.