How long did you grieve for the last pet you lost?

I had to say goodbye to one of my cats last Monday. It wasn't the first loss I've had, but it was the first time that I was there one that had to make the decision. The first time I was the one to sit with him at the vet during his final moments. Even now, a week later I find myself breaking down with grief in the quiet moments. The loss just seems to hit so much harder when you are the one making the decision about it. It's been a week and I can make it through the day now. But at night, at night it still feels like it was just yesterday he was curled up next to me.