So sorry to hear this mate. I’ve had to do it three times and never gets any easier. And nor should it, they are a member of the family. The important thing is be upset, be sad, but don’t feel guilty. Your dog has already had the best life ever, extended far beyond what it would have been in the wild by your love and care.
That cartoon made me cry in the waiting room at the dentist which made for an interesting conversation with the receptionist. Funny thing is it is right though. Dogs know when it is time and they’re okay with that. Not unusual for them to head off to a place of peace and slip away.
And as said above, the thing that your dog would want above and beyond would be for you to offer another furry friend a home and a refuge and a pack. They’re all different, but all equally special.
That photo of the sunset seems to have raised the dust levels in my room to an all-time high. God speed