As any reputable trainer or dog training book will tell you, canine learning is based largely on repetition. But one day you are tired or distracted and you roll through an intersection. Discuss the problem with your veterinarian before embarking on a behavior modification program. You may wish to be there for the dog's final moments, or it may be too difficult a task.
If you can't bring yourself to be there, do not chide or accuse yourself of letting your dog down; it is very difficult to predict how one will respond to the death of a loved one.
The telephone rings but you keep reading your book. Dog health symptoms such as this may not be related to those nasty little parasites after all. Sometimes the brightest dogs are also the most stubborn, so keep the faith and know that every dog, no matter how resistant, can be educated. As a last resort to solve a compulsive eating disorder, discuss drug therapy with your veterinarian. It is very difficult to imagine life without the creature that has given us such-joy and love over the years. If you plan to be present, try to bring someone along who can help you through this trying event.
Assuming that those habits are positive ones such as eliminating outside, coming when called, lying down and staying when told, and others - you will have what you want: a trained dog.