Norene and I both expected to be emotional basket cases when the day came, and I'm not saying we were not sad, but...
Riqui (Suncatcher's Periquita, officially) had a bout of congestive heart failure on January 3rd and the vet told us then "3 months... maybe 4" so this wasn't exactly "a surprise". With excellent care, she lasted through October, but in recent days she started huffing more, not exactly a cough, but respiratory. She also started getting foggy. She'd go outside on the lawn and seem not to know exactly why she was there. She was becoming incontinent, but... knew where the Puppy Pads were and what they were for. Friday when we took her to see the vet again, her tongue was purple. She was visibly struggling to breathe.
You always wonder "Am I doing this for my convenience?" but there's a flip-side to that coin: "Am I keeping her alive so that I, myself, won't feel pain?" In the end, we opted to take the pain to save her from it.
I suspect it's going to hurt a long time. Memories are like that, damn it.