An important lesson I learned from our office pet training session is this: No matter how well you know your pet, you do not know all other pets well.
This means that you should always take precautions when out and about with your pet when you know there will be other pets around. Though your dog may be the perfect angel off-leash, staying right by your side, you never know if someone else’s dog that is on-leash is about to lunge at your dog.
Some of us in the office who sometimes come and go with our dogs off-leash are working on getting into the habit of leashing them. They may behave well off-leash, but it is unpredictable whether or not another dog will appear along the way and bark, lunge, try to play, etc. With all dogs leashed, we can have maximum control over every situation that we are in.