Especially when the dog really "fits" you.
I had one for Four months. He got hit after he got away from my daughter.
I was totally in anger fits about the whole. I was and still to this day (18 months later) in agony.
Sure, we have another dog, Weimaraner-Boxer mix, just as outgoing, playful, annoying, obsessive with playing etc... Nearly the same dog personality-wise. It just isn't the same. Bryn, she will never be able to completely replace Cinnamon, he isn't replaceable. She takes her own-space.
Just typing about it is making me cry out of sorrow. Dammit. Why is it, that sometimes, the ones around the shortest, have the largest effect?
Just try to remember the good, it makes all the difference in coping.