Euthanasia?

Alright, I even hate asking this, or thinking about it, but I have a dog nearing her time here with me & I know there is nothing more I can do for her,or any vet for that matter. It is just breaking my heart. As I sit here I am about in tears. I have only had to do this one other time, but he was my daughter's dog.Kind of like my own though since they lived in my home & I provided for him.This may sound like a stupid question, but can you tell me how can I lessen the pain I have to endure when I decide to take that last trip to the vet with her? Of course I will stay by her side through the proceedure no matter how bad it will break my heart. Thank you all so much for any answers.