First, I want to tell you that I'm really sorry and my heart aches for you.
Six years ago our German Shepard starting have seizures. In a few weeks the seizures picked up in frequency and harshness. I came home one night and she didn't recognize me and walked in circles all night agitated and disoriented. My husband was gone that night and due back the next evening. In the morning she had a seizure that I didn't think she'd pull through. I was hysterical (I'm not a hysterical chick by nature) but this was too much. I called my husband sobbing and begged him to come home NOW. We had her put down that afternoon, day before Thanksgiving, and even now, six years later, I cry throughout that day. And, someone in my family inevitably comments about how this holiday the anniversary of putting our dog down...and I inevitably want to punch them for the reminder. I will warn you that it's not necessarily as easy as you may envision. The sleeping shot made our cat throw up and our dog's nervous whine (she had always been very vocal) was not completely silenced by the drugs.
Last year, a week before we left for Ireland our cat went downhill in 3 days time due to congestive heart failure. We had the vet come to our house to do it and we both cried like babies for the 48 hours beforehand. We took one of his white whiskers with us to Ireland and left it in the center of New Grange, a passage tomb. And again, we cried like babies.
I think a bond with a pet can be tighter than that with a human because pets just love us, no matter what. There's no judgment or pettiness, just love.