Charlie, for instance, is almost bursting with anticipation when he goes hunting at the moment - he is the physical embodiment of the feeling you get as a small child on Christmas Eve - he can't possibly stand still, he can't possibly go to sleep, its just too exciting!
In another parallel, I remember my father (a retired consultant psychiatrist and life-long non-dog-owner) noticing that my dog, Rufus, was very subdued after our other dog had died suddenly and remarking that there was no physiological reason why dogs, just like people, shouldn't experience grief and depression.
Some horses, however, just have a sense of humour. Today I was out trimming horses and after bringing in and feeding all the horses this morning, I left Andy in charge. I had a call in the afternoon to say that Felix had let himself out of the barn on 3 occasions. He had been for a walk round the house, eaten some lawn, topped some roses and pulled a couple of pot plants out. He was angelic to catch again, because that's half the fun - no point creating an impression if you aren't there to see it...He doesn't do this when I am at home, of course, but its just too entertaining to wind Andy up - or at least that's my (anthropomorphic) interpretation :-)