On page 57, under the heading "What we can do about stress in our dogs?" the first bullet says: "Change environment and routines whenever possible"
As others said, point of breaking routines is that if they come to expect things they get stressed if it doesn't happen, or doesn't happen in the way they thought.
For instance, separation anxiety is dealt with by changing routines. If you pick up your keys, get your coat, then shoes and then leave, they say pick up your keys, then step outside, then put them down and get your shoes, walk around a while then get your coat and keys, etc.
Change it up.
I can see how that'd address quite a few anxieties actually.
When foster dogs come here, they have to learn new routines and often want to "cling" to the foster mom as a lifeline. We try to break that in all instances, until the dog has settled in, and learned our household.
We have a routine of feeding that causes a great deal of stress in our dogs but we've tried to change it, and due to the amt. of dogs/fosters we feed 2x a day, it's difficult to keep that changing.