Its very difficult for a professional to give you an accurate opinion without being able to ask you a bunch of different questions. Like do you care if the dog sheds, do you want a dog that will be able to protect you, are you looking for a small, medium, larger or giant sized dog, or do you not care, will the dog be left alone inside and sleep inside, do you have an children that come visit you and should they be considered in your choice of dog, do you have a swimming pool and want a dog that likes water, if you plan on having your dog stay outside do you live in an extremely hot or cold climate, I could go on for another 20 questions but I think you get the point. Just from what you have told us, I would stay away from German Shepherds, labs, and other dogs that have high energy levels and need a lot of mental stimulation. They can definately become destructive if left alone for 8 hours on a daily basis. I currently own a 5 yr old male German Sheperd and they are one of my favorite breeds, but just are not appropriate for your situation. Like I said, I need some more info to give you a great answer but just guessing I think if you are interested in a large breed dog that can protect you and your home a Rottweiler may be a good choice. I also own a Bullmastiff and they are my favorite breed in the world. Mine is ok alone for 8 hours a day, but she has my German Shepherd for company. Bullmastiffs absolutely live for there owners and love them and want to be with them all the time. So a Bullmastiff my its self would probaly not be a good choice. If you were to consider getting 2 dogs though, there are not words that can describe what a good choice a Bullmastiff would be for single person living alone in a house. I have trained 100's of different breeds and owned 7 different breeds of dogs and none of them have the loyalty that the Bullmastiff does. Like I said though, if you are looking for just one dog that meets your needs, I would suggest you take a look at a Rottweiler. Another good thing is that they are a breed you will be able to find at a shelter or rescue. The fact that you have owned a large breed strong willed dog like a German Shepherd and you have done great with it, gives me the confidence to suggest a dog like a Rottweiler to you. Normally I would not suggest a Rottweiler to someone I have not met because of there need to be owned by an assertive experianced owner.
11 years of dog training specializing in protection, agility and behavior problems