@Kenna at the veterinary clinic where I worked before I retired we gave this poem to clients who had to euthanize a pet. I'm sure you've heard of the Rainbow Bridge but this one is specifically for euthanized pets. I'm sure it will make you cry - I always do every time I read it - but I hope it will also give you some solace.
If it should be that I grow weak
Then you must do what must be done
for this last battle can't be won.
You will be sad, I understand
but don't let grief then 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 don't want me to suffer so
the time has come, please let me go.
Take me where my needs they'll tend
but please stay with me 'til the end.
To hold me close and speak to me
until my eyes no longer see.
I know in time you will see
it was a kindness done for me.
Although my tail its last has waved
from pain and suffering I’ve been saved.
Please do not grieve that it was you
who had this painful thing to do.
We've been so close, we two, these years
don’t let your heart hold back its tears.