You're not the only one susceptible to a bad day.
Even small unwelcome changes in your pets' daily routines are enough to stress them out, and as it does with humans, stress can play a powerful role in animals' overall health and happiness.
"In animals, just like in humans, prolonged stress can lead to increased risk of additional physical and emotional disorders," says certified professional dog trainer Joan Mayer, owner of The Inquisitive Canine dog-training school in Ventura, Calif.
Common signs of stress include changes in appetite, excessive drooling, pacing, scratching, destructive chewing, urinating in inappropriate places and increased shedding.
"Another common sign, which often gets ignored, is stress panting, which is when the lips are pulled back on a horizontal plane," Mayer says. "You might also witness an increase in lip licking or yawning."
Changes in vocal habits are also cause for concern.
"Whimpering, whining or any other deviation from his or her normal vocalization pattern should cause the caretaker to take notice," Mayer says.
Of course, all dogs are different. What may be cause for concern in one dog may be perfectly normal behavior in another. Any change in your dog's daily routine or usual demeanor is cause for concern and should not be taken lightly.
"Be aware of your dog's stress signals. A sudden change in an animal's behavior when there is no apparent reason for the change should warrant a vet check," Mayer says.
Physical ailments and chronic health issues are a primary cause of stress in dogs, so your first stop should be the veterinarian. Any medical condition, from a mild case of fleas to cancer, can trigger a stress response.
If the problem isn't physical, it's probably situational. Poor socialization, improper training methods and lack of mental stimulation can cause severe stress in even the most good-natured canine.
"Dogs are very social animals and like to have company, so one common type of stress that dogs manifest is separation anxiety," says Edie Jarolim, author of "Am I Boring My Dog? And 99 Other Things Every Dog Wishes You Knew" (Alpha/Penguin, $14.95). "It's approximated that some 17 percent of dogs get so upset when their humans leave the house that they engage in destructive behavior."
Serious cases of separation anxiety often create a cycle of stress within the home, which further feeds the dog's symptoms.
"Your house is wrecked, and you get upset, causing the dog further stress when you get home; it's a vicious cycle," Jarolim explains.
Separation anxiety has its roots in boredom, but breaking the cycle requires a two-pronged approach: Provide anxiety-prone dogs with engaging distractions, and curb the human response.
"Provide toys that require dogs to work for their food, such as the Buster Cube, just before you leave the house. This keeps them occupied for as long as an hour, which is the crucial period after you leave," Jarolim says. "Then most dogs settle in and sleep for a good part of the day."
If your dog has a rough day, be patient. Don't overreact. Use positive training methods -- never coercion or aversion, which can lead to fear, aggression and biting. You may be frustrated that Rover chewed on your new shoes, but a calm response is the best response.
"Dogs get stressed when you're running around being stressed. Take a deep breath, and sit down for a moment or two. It'll calm you down, and it'll calm your dog down," Jarolim says.
Also, consider hiring a dog walker or springing for doggy day care. If your faithful companion spends the better part of the day alone, enlist a professional to help break the monotony. The extra exercise alone may be enough to defuse the stress.
"In general, dogs that are sufficiently exercised have far less stress, just like humans," Jarolim says.
Training and socialization classes also can help, by giving dogs the opportunity to interact with strangers, learn proper dog-on-dog interactions and investigate new environments.
"A common source of stress is putting a dog in a situation in which he or she is uncomfortable and expecting him or her to immediately adapt," Mayer explains.
Routine exposure to new experiences instills healthy canine coping skills and lets owners learn what to expect from their four-legged friends.
"Treat animals as living creatures that have likes, dislikes and emotions like humans," Mayer says. "If you learn more about how your animal communicates, then you can make the necessary changes to help him or her adapt, cope and enjoy his or her surroundings."