I've posted this poem before it might help
If it should be that I grow weak
And pain shall keep me from my sleep
Then you must do what must be done
For this last battle cannot be won
You will be sad I understand
But do not let this stay your hand
For this day, more than all the rest
Your love for me must stand the test
We've had so many happy years
What is to come can hold no fears
You'd not want me to suffer so
The time has come, please let me go
Take me where my need they'll tend
And please stay with me until the end
Hold me firm and speak to me
Until my eyes no longer see
I know in time that you will see
The kindness that you do for me
Although my tail it's last has waved
From pain and suffering I've been saved
Please do not grieve it must be you
Who has this painful thing to do
We've been so close, we two these years
Don't let your heart hold back it's tears
I hope it helps a little