The author says that after having a resource-guarding dog, he created guarding issues in his later dogs by always feeding them separately, never feeding chews together, etc., so they didn't learn appropriate skills. And people who have previously had reactive dogs may find themselves avoiding other dogs and feeling anxious about meeting them when they have a perfectly sociable dog who would get on great with other dogs.
I've often wondered how having Jasper will affect my handling of future dogs. I once saw my friend's placid lab get a bit growly when my friends daughters tried to wrestle a sock off him and I immediately called him to me and gave him a treat in exchange for the sock. My friend wasn't best pleased as she was sure he'd now hunt down every sock he could find... I think the hardest part might be relaxing when 'next dog' is sprawled over my lap on the sofa and I want to move to allow blood flow to my legs....
You do quite often see people say 'I've had lots of dogs before but never one who did this.' It must be quite hard to move beyond your previous dogs and accept that different rules now apply.
I do rather like the last bit:
I'm certainly not as knowledgeable and skilled as professional trainers but if I'd had an easy dog, I might never have got past 'Feed them after you so they know you're the boss'We work with many people who we helped when their former dogs had significant aggression issues around other dogs and who then get a new pup when the time comes, often years later and who return to us for puppy classes instead of reactive dog classes. These people make the most amazing dog parents as they’ve learned so much from their difficult dogs and they have such great skills. Many of them are as knowledgeable and skilled as professional dog trainers and it’s all thanks to the ‘previous dog’ who they worked so hard to help. That difficult and much loved dog lives on in the things they taught us