I apologize in advance for the length of this, but I thought it might help you to hear more background about my own story. It's just another perspective that might hopefully help in some way. In no way am I trying to change your mind about anything, but am offering this as in an anticipatory sort of way, to hopefully lessen any chances of future regrets you might have, and ONLY because your decision is bothering you still. (everyone else was writing at the same time as me, so I'd missed seeing what they'd already said and have since edited only bits of this)
For
me, if my girl hadn't been so obviously dying (no longer able to get up; refusing to eat at all on her last day - only one day of this, with the day prior eating much less than normal, but still eating), I couldn't and wouldn't have done it. I'd spoken to her 2 vets about possible, likely and not-so-likely pain issues and also spoken to a friend of mine who's a retired human doctor (who's seen lots of dying people) about same. I was trying my hardest to not take her life away before she was done living it, yet also trying to spare her
undue suffering. And that's where I may differ from some others about what "suffering" means to each individual.
While most of us don't want to have to live through great physical or emotional pain, a certain measure of each is pretty much inevitable for most of us before we die, and many of us also 'suffer' with various pains throughout our lives (I know I have), so I don't believe that NO suffering whatsoever is even an option for most of us, unless we have a sudden, fatal accident, and even then, it depends. I think it becomes more a question of just how MUCH suffering one can take or allow. That was part of the reason I also tried to weigh this decision against what many
humans go through when they're dying from different diseases/conditions. And since my Mother had been hospitalized (for half a year) and died not too long before this, I had a ready example at hand of the same sort of thing. Despite her many, awful conditions/diseases, my Mother wasn't ready to die sooner than she did. Just as I couldn't have taken
her life before it was very clear she wasn't going to make it (had I even had this choice) because of what my Mother was like, no more could I do this with my beloved girl - the same ethical standards applied. So for me, it became more about the critical question of trying to get the timing as good as is ever possible, carefully trying to measure and balance any pain issues along the way. And we had things on hand (from her vets) to do this for my girl, some of which I used in her last 2 days.
But this was
also because I knew my girl inside and out, and so knew she was a fighter (like my Mother had been), so it would have equally felt like a betrayal to her if I'd acted too soon. Since she'd (we'd) been battling her progressive kidney disease for many years already, I knew she'd keep fighting to stay alive until she no longer had a choice. And of course, I had to respect that, because it was HER life, not mine. Her needs superseded mine. Had she not been like this, though, my considerations would have had to have been different. Additionally, I'd also had various communications done (by different communicators, who all came back with the same answers about this), both near to her time and through the years before this, where not only she, but even her (passed) brother had said that I
would end up eventually having to help her cross the veil. So everything in total was taken into account as I went through this with her. Were it not for all this, I don't know how I would have coped with this decision at the time.
However, her brother Sabin had already taught me, through his terrible death years before, that this can also be a good, and sometimes much better thing, depending on the individual and the circ*umstances. I was totally unprepared and a real greenhorn with this kind of thing back then, and he did suffer too much, too long, even for him and who he'd always been (an even
bigger fighter!). I'd made my big mistake with him... and vowed never to be quite that ignorant and uninformed again in matters of life and death. But I'm sure I'll still make my share of mistakes, as everyone does. And btw, Sabin's cancer had metastasized to his lungs, too, and extremely rapidly. As well, it was mere
moments after I finally gave in and accepted that he had to leave, that he did. As Denise mentioned, often this IS all they're really waiting for. (with my girl, that was different, as I accepted her condition earlier on)
Despite all this, it wasn't any easier.....only different. In fact, it became even MORE important for me to do my very best (so even more pressure), and I still wasn't totally w/o some guilt and regret afterwards, but that has for the most part subsided some now. This is how impossible it can feel, no matter how 'prepared' one might be.
It might be better for you if you can just try to accept that you
will feel "crazy", for as long as you're going to and that it's acceptable to feel that way. That doesn't mean you are, only that you feel that way. It's a natural part of both anticipatory grief and 'after'-grief. When you love someone, there's no getting around it. You can no more "keep from" feeling crazy than you can from loving who you do, when you know you have to give up their physical presence in your life. You will handle this the same way we all do - in your OWN way, which will be the right way for YOU, no matter how awful and confusing it feels. How you can do this is just as individual. (the point of my story above) Personally, I found that focusing exclusively (except for basics) on whatever I had to do for my girl gave me the most strength to get through each day, each moment. It was an honour and privilege to serve her and provide whatever I possibly could on every level I could, even while I was falling apart at the seams. At least I knew I was making the most of her remaining time with me and wouldn't regret that. If there's any time to try one's best to live as cats try to teach us to ~ in the moment ~ it's at times like this.
But that doesn't mean you have to be all alone in this, because we're all here to share what it's like and to understand all those feelings of helplessness, sorrow and more, wherever we can.....usually very easily.

Let us know how you and Babe are doing, but only IF you can, or want to. We'll be here, whenever. Holding you and Babe in our hearts.......