Answer:
Well, it's easier to move on from it to stop thinking about it, or just get another dog that kinda looks like him
Step-by-step explanation:
1) Forgetting about the dog is not easy, but you will just forget him easier by removing every trace of your dog (not by removing everything your dog touched) but by removing things that's about him (and cleaning marks from him)
2) Getting another dog it could make you cry, but it's basically like having him again, he may not be the same but it's the best way for you moving on
(I'm not the best at stuff like this, so if this doesn't work (If it's to risky, like you won't be able to move on because of this please don't try this, get real good help))