Yellowted,
My girlfriend is a vet. technician, and has done various surgeries on many animals over the years. one thing see sees far too often is owners who keep their pets alive when they are suffering terribly, because the owner cannot say good bye.
While this is natura,l keeping an animal who is in pain alive because you cannot let go is not love. Animals cannot cope with or express pain like humans, and far to often my girlfriend sees them suffer beyond belief and the owner brings then to the clinic demanding the vet do everything even if it just prolongs the agony.
The death of any creature is a sad thing. I have a cat who is 17 and she is beginning to fail. The last time Bobbi, my girlfriend left the house to take her to the clinic I said, don't put her to sleep unless you call first.

She looked at me and said "I will not let her suffer, if there is nothing I can do to releive her pain I will put her down." She said that was only ethical and I could take her to another vet if I disagreed.

Well the cat was able to be helped but I just noticed again that she seems in distress. I may have to have Bobbi bring her to work at the clinic tomorrow.
I do know that some vets do acupuncture to releive pain in animals, even small animals, and as it will not cure cancer, it might ease the animals pain. You may ask your vet if this is poossible with such a small animal.
But remember you have to act in the best interest of the animal. If you do need to put her/him down, you can wait a while, mourn your loss and then get another pair of pets and start the life cycle all over again.

Sometimes it is difficult to sort feelings out, but do not keep the animal alive just for YOUR benefit.

One other thing, after losing several pets through the years, I find comfort in burying them, not leaving them at the vets to be disposed of. I have even buried my sons gold fish. There is something soothing about returning a crature in its natural form to the earth, where their remains will nurture and grow grass and plants and trees. There is a cycle of life and we must learn to respect it. Sometimes I wish we could help ease the pain of terminally ill humans they way we do animals at the request of the person. However that is where the value of the human soul comes in and we are taught, properly I believe that we can ease animal suffering we must treat the human body and soul differently and allow only God to make all decisions regarding human life and death.

God speed and think about what is best for your pet's, you are responsible for them, do not makle them suffer.