I know what you mean. My Crystal is so good and then when she gives me the 'sad eyes' for one more little treat at night, I usually give in (she'll be 14 in June so the way I feel is, I've watched her diet pretty well for so long I don't think it's going to hurt her.) We are lucky to have our dogs and I remember the saying "Dogs are not our whole life but do make our life whole" and I would add so full of joy.
My aunt and uncle owned a sheltie and she was the most gentle natured little dog I have ever met, she sadly died a few years back and is still missed greatly.