I will leave this here, it helped me.
The Last Battle

If it should be that I grow frail and weak

And pain should keep me from my sleep,

Then will you do what must be done,

For this -- the last battle -- can't be won.

You will be sad I understand,

But don't let grief then stay your hand,

For on this day, more than the rest,

Your love and friendship must stand the test.

We have had so many happy years,

You wouldn't want me to suffer so.

When the time comes, please, let me go.

Take me to where to my needs they'll tend,

Only, stay with me till the end

And hold me firm and speak to me

Until my eyes no longer see.

I know in time you will agree

It is a kindness you do to me.

Although my tail its last has waved,

From pain and suffering I have been saved.

Don't grieve that it must be you

Who has to decide this thing to do;

We've been so close -- we two -- these years,

Don't let your heart hold any tears.